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H$' : . jN i.'< .^ CANADA PUBLIC ARCHIVES ARCHIVES PUBLIQUES 1 1 !l ff iM K' m 'I m- pK ' -ffe^*'^^*^ • • ON Veterinary Anatomy 'f ^i^ FOR THE USE OF STUDENTS AT THE O. A. C. BY J. HUGO REED. Prof. Veteri7iary Scieyice. guelph: o. e. turnbull, printer and binder, 1900. ♦ • > ^L /■■■"I \ SHORT NOTES ON VETERINARY ANATOMY. yeterinary means belongino^ to beasts of burden. Anajtomy is the science of organization. Animal AiT aiomy or Zootom y, has for its object the investiga- tion of the animal frame, an investigation conducted by mechanically dividing it into its compotent parts and studying their form, structure, attachments and relations. Anatomy may be comparative, special, or transcen- dental, according to the scope and ultimate object in view. Thus, if more than one species of animal be under consideration, the comparative anatomist takes note of the various deviations and similarities; but if the investigations be confined to one species of animal, as in human anatomy, the subject then becomes special. When special anatomy leads to the thorough investi- gation of one single variety, for the purpose of comparing other classes with it, the subject of such special study is called a type. Comparative anatomy, therefore, is not studied by the indiscriminate comparison of one type with an- other, but by referring them to certain types or stand- ard. The horse is taken as the type by the Veterinary Anatomist, embracing as it does the structural investi- gation of the whole animal kingdom. Comparative anatomy is closely related to the science of Zoology, the latter science aiming specially at the attainment of a scientific method of classification. Transcendental, or Philosophical Anatomy, seeks for analogies and developmental facts, which may guide the investigator in his search after primary anatomical types. Since^the prosecution of such a study must assume a more or less profound knowledge of Com- parative Anatomy w^e merely mention it in passing. -4— If we consider a portion of the animal body with respect to its form, si/.e, relative position or strnctnre, we are said to consider it anatomically; but should we enquire into the use or function of such a part, or seek- to learn the changes undergone in it while in a living condition, then we are investigating physiologically. This is a general distinction between anatomy and physiology, l)ut it will readily be seen that they are to a great extent bound up in one another, since l)oth the sciences must lend their aid to afford a complete description of any given organ or part. The branch treating solely of structure and form is called Mor- phology. Histology, or minute anatomy, treats of tlie intimate structure of the tissues or materials of which the various parts of the body are composed. As the tissues present various characteristics invisible to the naked eye the histologist uses the microscope largely in his investigations. Embryolog}', from an anatomical point of view, is a science considering the various appearances presented by an animal after each of the many successive stages of development, from when it first appears as a mere speck of vitality until it has acquired the general characteristics of a perfect animal. Anatomy in all the above mentioned branches deals only with normal or healthy material ; but should such material be in a diseased condition, the consideration of the changes it has undergone is termed Morbid Anatomy. Surgical Anatomy embraces the description and investigation of such parts of the body as are most liable to 1)e involved in vsurgical operations. Anatomv ma}' be descriptive or practical. In the former the student relies on books, diagrams, lectures, etc., for his information; in the latter he verifies de- scription by actual dissection and demonstration of the various structures in question. Veterinary Ana- tomy, in the full sense of the word, includes the anatomy of all domesticated animals, and is therefore a branch of Comparative anatomy, and the animal referred to as its type is the horse, the anatomy of which (or Hippotomy) we will consider, while the deviations from this type in other animals w-e will notice as fully as the scope of our work will permit. \ '• : Anatomy is a very important branch of study. It is part of the foundation upon which a knowdedj^e of disease must be has 'd, for if we (U) not understand the normal or healthy structure of a part we cannot ap])re- ciate the changes which take place in disease. To some, anatomy appears a dry subject, but apart from the practical object we have in view, much interest may be excited by the beauties of nature's designs as they be- come unravelled step by stc]). In this course we cannot give much more than an outline, but v»ill endeavor to give enough to enable you to understand the nature of the diseases and injuries that we study. In addition we consider that the knowledge of ana- tomy the student will attain here will enal)le him to study the points, characteristics and conformation of animals with greater ease and more thoroughly. The animal kingdom is divided into the sub-king- doms Invertebrata and Vertebrata. As the names imply, the latter is distinguished from the former by its members possessing a vertebral column or back bone, which forms, as it were, the axis of a bony frame- work, supports the head, and is placed dorsally, or in the region of the back, extending from one end of the body to the other. It is pierced tliroughout the greater portion of its length by a canal called tlie neural canal, which is continuous with a cavity in the head called the cranium. These cavities are occupied b}^ centres from which radiate a large series of nerves ternitrd the cerebro-spinal system. Underneath the backbone there is a second series of nerve centres, called the sympath- etic system. Thus, in a vertebrate animal there are two systems of nerves whose centres are separated by a partition of bone. The remaining portion of the animal body may be regarded as a second cavity, or canal, which contains, in addition to the sympathetic system of nerves, the alimentary and the haemal sNstems. The former runs the v^^hole length of the body, being a canal which gives passage to the food, the latter con- sists of a series of tubes by which the blood passes through the body, both systems being supplied with many accessory organs. In the higher invertebrate animal we find no back bone, no neural canal, and no cerebro-spinal system of nerves, but the visceral canal exists and its contents — b— correspond mostly with the structures found in the vertd)rate. If we eliminate from the vertebrata all the classes but the two hij^hest — the mammalia and aves — we shall further localize our subject, since the two classes con- tain rtll the animals which, as a rule enj^a^e the atten- tion of the veterinary anatomist, to whom the first of the two is of by far the j^rcater importance. It is sufficient to state that mnmmalia are characterized by the females beinj^ provided with an apparatus which sup|*lies milk for the nourishment of their young after birth. Aves (or birds) are distinguished from mammals by their producing their young oviparously, or by hatching tlie egg outside the body. They never suckle their young, and have a covering of feathers. Descriptive Anatomy. Osteoloi^y is the term applied to that section which treats of bones. Arthrolos:y, a consideration of the joints. 31 yo logy, the muscles. Splanchnology, the viscera. Angiology, the circulatory and absorbent system. A^e urology-, the nervous system. Aislhesiology, the organs of sense. Embryology , of the animal before birth. The terms analogy and homology are frequently used, and the following distinctions betvseen the terms may be noted: Organs are said to be analogous when, though differing in structure, they perform the same function, but when their functions are different, while in the broad sense they correspond in structure or form they are said to be homologous. Thus, the middle finger of the human hand is the homologue of the an- terior digit of the horse, because they have the same general struction and relation to the rest of the limb; but as the functions they perform are quite different, they cannot be termed analogous. And then the lungs of a mammal are analogous to the gills of a fish, for though they differ widely in structure, position and form, and are therefore not homologous, their ultimate use is the same, each of them being an apparatus in which is carried on the process of purifying the blood. I \ \ ■7— the I Osteology. Struct lire of Bones. Bones are hard, yellowish white bodies which form the internal skeleton, vjive attachment to soft structures and are of various sizes, forms and densities. In the linihs the bones are-gen - erally more or less cylindrical, with expanded extrem- ities, they supi)orL the body, afford leverage and attach- ment to the muscles and form the basis to all joints. Where cavities such as the cranium, chest and pelvis, enclose viscera requiring protection and sup])ort, the bones assume a flat, expanded form. Living bone is bluish white, insensitive and elastic; exposed to the air it becomes diseased, assumes a black or livid hue and is extremely sensitive and painful. The teeth excepted it is harder and of a higher specific gravity than any other animal tissue. It consists of inorganic salts deposited in a basis of animal matter. It owes its density and hardness to the former, its elasticity and tenacity to the latter, the union rendering the tissue solid and elastic. By steeping bone in dilute hydrochloric, or other strong mineral acid, the earthy matter is dis- solved, while the tough flexilde animal cast is left. If we expose bone to the action of heat we get rid of the animal matter, while a white, brittle, earthy, chalky substance is left, retaining its original shape. The relative proportions of animal and earthy matter vary at different periods of life. As an animal grows old the animal matter decreases, hence the bones of very old animals are brittle and easily fractured. The animal and earthy proportions do not vary in true bone tissues, but there is a gradual filling up of the cavities originally occupied by fat cells, thus condensing the bone. The earthy ingredients consist chiefly of car- bonate and phosphate of lime, the animal matter of cartilage and connective tissue, vessels, lining mem- branes and a quantity of fat. The following is the average analysis of th? femur of a six year old horse : Phosphate of lime (with traces of Fluoride Calcium). ..54.37 Carbonate of lime 12.00 Phosphate of magnesia 1.83 Soluable salts 70 Cartilage 27.99 Fat, etc 3.11 100.00 — 8— The bones of young animals may have too great a proportion of animal matter, when they give way under the weight, as in rachitis. The degree of hardness varies not only with age but also watli the class of ani- mal ; the bones of birds being white, hard and brittle, especially those of the wings and legs, whereas fish bones are soft and flexible. They also vary in different parts of the same skeleton, the petrosal bone being the liar, lest one in the body while the ribs are soft and flexil)le. The leg bones of a thoroughbred horse are more com- pact than those of a heavy cart horse. The latter are larger but do not weigh as much in proportion, because the shell or outer layer is more expanded and thinner, affording greater surface for muscular attachment; whereas in the thoroughbred a greater density of bone is necessary to withstand the immense concussion of speedy action, therefore the bor.es are increased in thickness of shell, affording greater strength without apparent increase of size. It Ol ol cl n| Osseous Tissue. In bone there are two modifications of texture, the compact and the cancellated. The former, hard, dense and ivory-like, is always situated externally; the latter, porous and spongy, lies within. Compact tissue appears uniformly dense, but if we cut a bone transversely and examine with a microscope it is found to contain num- erous small openings called Haversian canals for the transmission of blood vessels, which run in a longitud- inal or slightly oblique direction, opening on either the outer or inner surface of the iDone. They also have many transverse branches of communication which are often of greater diameter than the trunks. These canals are from 1-200 to 1-1000 of an inch in diameter and surrounded by concentric layers or lamella of bone. Among them can be seen small dark bodies (lacunae) filled with fluid from which pass radiating lines (canal- icula) which establish communication between the Haversian canals and the lacunae. On the external part of the shell of the compact tissue of long bones are several concentric osseous layers (the peripheral lamella) passing completely around the shaft. There -9— I is also a corresponding concentric disposition of layers on the inner or medullary surface. Both these systems of lamella are in a great measure destitute of Haversian canals, and are supplied with nutritive material by means of lacunae and canalicula as in the compact tissue generally. Each Haversian canal may be considered a vascular longitudinal centre, round which successive concentric layers of bone are arranged so as to form a dense cylindrical ossicle. Series of these are repeat- ed, and uitited by lamella destitute of canals, but with numerous canalicula and lacume and called the con- necting or interstitial lamella, the entire structure being encircled by the external peripheral lamella. Cancel- lated or spongy tissue is always situated internally. It consists of a large number of fragile bony plates with spaces between them called the cancelli There are lacunae and canalicula, but no Haversian canals, their place being taken by the cancelli. (In the bones of the cranium this tissue is called the diploe.) Covering" of Bone. The external surface of every bone is covered by a tough, fibro-vascular membrane, the periosteum, ex- cepting where tendons play over the bone, and its arti- cular surfaces, upon which there is a layer of cartilage. The periosteum, firmly adhering to the bone, contains minute blood vessels which are thickly distributed be- fore entering the osseous tissue, and it contains two layers, an outer one, fibrous and protective, and an inner one, which consists of fine connective tissue and contains bone-producing cells. The inner lover is con- tinued into the Haversian canals, a layer of cells also existing between the canal w^all and the contained ves- sel. It affords support and protection to the bone and attachment to tendons and ligaments which frequently become continuous with it. It varies in thickness, being dense and strong on bones nearest the skin and liable to injury. In the young animal it is thicker and more vascular than in the adult. Blood vessels which ramify in the periosteum pass directly to the bone. The external surface of a bone is always studded with num- erous foramina through which these enter. The perios- IHIMHBMi —10— teuni, owing to its inelasticity, is, when inflamed, tlie seat of intense pain; and should any part of it be strip- ped off, there is every probability of the denuded bone dying and exfoliating. It is most vascular near the joints where it tenninates by joining the articular cart- ilage, or passes to the next bone, but it never covers an articular surface. The internal, or maduUary cavities, are lined by a more delicate vascular membrane, the endosteum or madullary membrane, which is prolonged into the cancelli and Haversian canals. It is very thin, consisting of delicate areolar tissue, fillament from which serve to support the marrow, the nutrient or madullary arteries entering the bone by the so-called nutrient foramina being chiefly distributed in it. The periosteum covering the bones of the cranial vault is called the pericranium. Contents of Bone. Marrow is a soft yellow fat, the cells of which are supported by areolar tissue, it is contained in the ma- dullary canal and cancelli and thus fills up the cavaties of the bone, containing many blood vessels. The large bones of most birds in adult life contain air in- stead of marrow, biit in the bones of a mammal in per- fect health there is a considerable quantity of the latter which becomes diminished in disease. In the bones of the foetus there is little or no true fatty matter, but a transparent redish fluid, the red marrow is found, it couvsists of "specific myeloid cells containing numerous nuclei. Blood vessels are numerous in bone tissue, the arte- ries ramifying in the periosteum enter by the Haver- sian canals, the madullary artery enters by the nutrient foramen, and the arteries of the cancellated tissue pass through foramina situated near the articular surfaces. The veins are numerous and do not accompany the arteries, but occupy separate canals, the diploe in the cranial bones contain large dilated veins. Lymphatics and nerves also exist in bone and its coverings. Classes of Bone. Bones are classed as long, flat and irregular. Long or cj'lindrical bones are found in the extremities, where !■• ] ^11- ned, thti >e strip - led bone near the ar cart- overs an cavities, ane, the olonged ry thin, it from rient or o-called . The vault is hich are the nia- cavaties i. The 1 air in- in per- le latter :>ones of T, but a ound, it imerous lie arte- Haver- lutrient ue pass Jirfaces. any the i in the phatics they serve as levers and pillars of support. For des~ cription a long bone is divided into a centre or shaft and extremities. The shaft is C3lindrical and consists of a shell of compact tissue of varj-ing thicknesses, which encloses the cancellated tissue and madullary canals, and is pierced by the madullary or nutrient foramen. It is smallest in the centre, expanding towards the extremities and is circular, oval or prismoid in form. When a long bone is placed nearly vertically under the body, the internal wall of the shaft i,s usually the thickest, when obliquely placed the thick portions of the shaft correspond with the line through which the centre of gravity passes. lyong bones are never straight, they may be twivSted, as is the humerus, and if bent are generally convex on tlieir exposed surfaces, the shell being thickest on the concave side. The ex- tremities of long bones always exceed the shaft in cir- cumference and are remarkable for tlieir irregularity of outline, they are expanded and roughened to afford surface for the attachment of tendons and ligaments, their protuberances also materially increasing the me- chanical power of muscles by serving as pulleys over which the tendons play. The extremities are composed of cancellated, with a thin layer of compact tissue, the cancellated getting gradually less dense towards the centre of the shaft which is occupied by the madullary canal. While the extremities exceed the shaft in diam- eter tlieir weight is not relatively greater, their increase in size being due to a diffusion and expansion of ma- terial, not to an addition of substance. This arrange- ment lightens and strengthens the bone besides filling its cavities with a fatty buffer to resist concussion. The hardest part of a bone is usually the thin portion lying next to the articular surface, it is only found when the bone is fully developed and it rests upon a series of arches formed by the cancelli ; this thin layer is covered by cartilage. Excepting on their articulating surfaces, the extremities of long bones are copiously pierced by foramina, which chiefly transmit blood- vessels to and from the interior. Flat or tubular bones exist where mechanical action is at a minimum and help to enclose cavities containing important organs. Thus the cranium protects the brain, —12- the scapula and ribs protect the respiratory organs and the heart. Flat bones are composed ot two thin ex- panded plates of compact tissue, rarely quite parallel to each other and enclosing a cancellated structure be- tween them. The internal is considerably harder than the external plate, but not so thick and tough, the outer being more elastic and less liable to fracture. The connecting cancellated tissue is plentifully sup- plied with blood vessels. In the bones of the cranium the compact plates are called the tables and the spongy tissue between, the diploe; the tables also in some fac- ial bones may be widely separated with air cavities be- tween them. Irregular bones include all that are not classed with the foregoing. They are found in the vertebral column in the skull and also in the limbs. They usually pos- sess man\' angles and indentations with surfaces for articulation and tendinous. attachment and consist of a fine, dense, external case of compact bone, enclosing cancellated tissue. In proportion to their size they present a much larger extent of articular surface and greater mechanical strength than any other class. tl d Surfaces of Bone. Mi Si } I No bone is strictly geometrical in form, although to a casual observer some may appear so. The chief ir- regularities consist of certain eminences and depres- sions, a knowledge of which is one of the chief requisites in the study of osteology. These are either articular or non-articular; the former being clothed with carti- lage and assist in forming joints. Non- articular emi- nences are found on V xternal surfaces of most bones and receive the att ' xicnt of tendons and ligaments and they are frequently named from their real or sup- posed resemblance to some object. The term process may be generally ; pplied to prominent elevations which are not necessardy non -articular. A spine is an elevation which tends to become pointed ; a tubercle is a small, blunt elevation, which if more developed would be called a tuberosity, while the name trochanter is applied to the largest and most prominent of these. A crest, or ridge, implies a roughened line or border. Non -articular depresssons passing completely or partly "j iiiwiMHw m w w — lo- rgans and 'o til in ex- ile parallel ucture be- arder than tough, the fracture, 'ully sup- e cranium le spongy ionie fac- ivities be- sed with al column Jally pos- rfaces for sist of a enclosing size they rface and iss. hough to chief ir- 1 depres- ■equisites articular th carti- lar emi- )st bones ganients or sup- process IS which - is an )erc]e is Jveloped >chanter •f these, border. * partly 1 3 through a bone are called foramen, canal, aqueduct or meatus, the first name l)eing the most used. Blind cavities on the surface of a 1)One are called fossa. The terms notch and fissure indicate depressions or grooves which tran.smit various structures. When a depression leads to two or more foramina it is called an hiatus. Articu/ai'- Eminences. A caput, or head, is a more or less semi-spherical project on supported by a rough- ened and constricted cervix or neck. An ovoid convex- ity is called a condyle, Condyles are often found in pairs, the articular surfaces of which mav be continuous or separated. A trochlea is an articular surface pre- senting a pully-like appearance. Articular Depressiiws. A glenoid cavity is shallow, and may be cup-like. When a cavity is deeper it is called cotyloid. The term facet is applied to articular surfaces large or small which are not well marked as either elevations or depressions. D*^ elopment of Bone. Although th oones of the foal, calf, and young of other large quadrupeds posses greater solidity at birth than those of the human infant, yet they all nass through certain progressive stages of development be- fore arriving at the degree of density which they ulti- mately possess. The tracing of future bone is recog- nized about the seventh week of foetal development in local collections of soft granular gelatinous pulp which becomes gradually flooded with nucleated cells, held together by an op ique intercellular basis, or matrix, which with the cells equally distributed through it forms temporary cartilage, a material closely resem- bling ordinary gristle. Bone is developed from temporary cartilage. The process of ossification begins at certain fixed points called ossific centre, and graduallv spreads. In long bones there are three ossific centres, one in the centre of the shaft called the diaphysis and one at each extremity called the epiphysis. When any large process is super- added it possesses a distinct ossific centre called an apophysis. As ossification commences in the shaft, there are for some time after birth, intervening portions -14— ! I ' I I III > I I of miossified cartilage, marked by the deep ring in the long bones of younj; animals; they disappear at vari- able periods, the portions of bone hitherto imperfectly united becoming cc»nsolidated into one firm mc:ss. The bone increases in length by the growth of the unossi- fied ring, uniting the shaft and epiphysis, until the ring fills up, whe:i growth is completed. Should an epiphysis unite w^itli a diaphysis prematurely by accel- eration of the process of ossification through disease, gro\\th being thus arrested, the bone will be shorter than its fellow. The shaft of a long bone increases in circumference by deposits of new bone on its external surface derived from the inner layer of the periosteum (which has been termed the osteogenic membrane). In the periosteum there are two layers, an outer, strong and fibrous, and an inner, soft and containing osteo- plastic cells which produce layers of new bone. In flat bones ossification usually radiates from a centre and is directed by the membrane investing each sur- face of the bone; some of them possess numerous apop- hysis. Ossification is completed in some bones much earlier than in others and at birth those which are required for support and progression are farthest advanced. The bones of the cranial vault are developed from membrane (not from cartilage). In early foetal life the brain is covered by two membranes closely united, viz. the pericranium and dura -mater; between these, bones become developed from radiating ossific centres. This may be termed intramembranous as opposed to intra- cartilaginous ossification. The Skeleton. By the term skeleton is generally Understood the bones of an animal held in their proper positions by legiments or by wires or screws. The former is called a natural, and the latter an artificial skeleton. The majority of bones exist in pairs, but there are excep- tions, as the vertebra, sternum and some of the bones of the head. Anatomists differ as to the number of bones in the skeleton, but for all practical purposes it answers to number them as 216, or including teeth 256. In speaking of the anatomical position and relation of bones as to other structures, continual reference is n II \ nng in the 5ear at vari- iuiperfectly nirss. The the unossi- is, until the vShould an ly by accel- igh disease, be shorter increases in its external periosteum brane) . In 'ter, strong ning osteo- bone. In '■ a centre ? each sur- irous apop- luch earlier equired for loped from ?tal life the niited, viz. iese, bones -es. This to intra - rstood the >sitions by r is called on. The ire excep- the bones umber of urposes it eeth 256. i relation erence is With reference to supposed to lie as —15— made to imaginary lines or planes, quadrupeds imaginary planes are follows: A longitudinal median vertical plane descends through the centre of the head, vertebral chain and trunk, midway between the right and left extremities to the ground, dividing the body into two exact halves. Right and left vertical planes are placed parallel to the former, but external to the body. At right angles to these an anterior vertical plane is placed in front and a posterior one behind. A superior horizontal plane lies above the body between the anterior and posterior planes, while parallel with the superior is an inferior horizontal plane placed under the feet. The external surface of an organ or region is that which faces the laternal plane on the side where the organ is situated; the internal surface faces the median plane; the an- terior surface the anterior plane and the posterior sur- face the posterior plane. The superior and inferior surfaces are those facing their respective planes. This imaginary index may be applied to any particular region or part as well as to the whole body. Modifications of these terms are used when it is required to point out the precise situation oi a structure. For example, take the anterior limb and suppose it encompassed by the planes as described. If we wish to describe the situ- ation of any object on the upper part of the laternal region, the term supero lateral would be used If the object were on the lower lateral part, then we would say the infero lateral, or to be more explicit we would say infero external or infero internal according to whether the object be on the external or internal part of the inferior region. Similar modifications are used in speaking of the anterior and posterior surfaces. Supero anterior means the superior part of the anterior region, antero superior and anterior part of the superior region. For description, structures (especially bones) are divided into two or more parts. Thus we allude to the superior, middle and inferior third of a part. The end of a structure which is nearest to the vertebral column is often termed the proximal end, while the end furthest from the column is called the distal end. For the purpose of description the skeleton is usually -16- V •X I 1 ! ] i li'i t ', :i' it if it (Uvifk'd into Iiead, trunk and extremities. The trunk amsists of the vertebral column, ribs and sternum. Vertebral Coluinii.— (Lt. Yerto to turn.) The vertebral, or spinal column may be considered the foundation of the skeleton from which all other parts proceed. It extends the whole length of the l)ody and consists of a series of single bones termed verte- brie and is divided into five regions, viz., the cervical 7, dorsal 18, lumbar 6, sacral 5, and coccygeal 13 to 20, respectively the regions of the neck, back, lions, croup and tail. While all pos.sess certain points of confirm- ation in common, special peculiarities distinguish the vertebrae of any one region from that of another. Ver- tebrae are either true or false. True vertebrie possess certain typical parts and they never, in health, unite by ossification, while false vertebrae either do not possess the essential characters of true, or they may so unite. True Vertebrae. A true vertebra consists of a body, arch, notches; spinous, transverse and articular processes. The body is the solid block of bone on which all the other parts are built and it is situated below the spinal canal, its anterior surface is convex and its posterior concave. The upper surface is flat or slightly concave, its inferior surface convex and sometimes terminating in a spinous process. The arch rises for the supero-lateral surfaces of the body by two processes of bone termed pedicles, from each of which a plate of bone, the lamina, expands and passes inwards, their union in the median line completing the arch which encloses the neural canal or spinal foramen. The notches are four in number, two anterior and two posterior, so placed that those of the anterior sur- face of one vertebra correspond with those of the pos- terior surface of another, thus forming a large opening, the intervertebral foramen, which gives passage to the spinal nerves and blood vessels. Each true vertebra except the first two cervical ones has four oblique or articular processes (zygapophysis) on the superior and lateral parts of the arch. The faces of the anterior of these processes are directed upwards w bfl ^pi at >*n«<(iMinW«*M«MN \ —17— I'fie trunk iirii.j considered 'ch all other of tlie body rilled verte'- the cervical •al 13 to 20, ions, croup of confirm - iii^^iiish the ther. Ver- irie possess Ji, unite by "ot possess so unite. 1, notches; The body other parts ^1 canal, its )r concave, its inferior a spinous ■1 surfaces ^1 pedicles, a, expands edian line 1 canal or terior and erior sur- f the pos- - opening, ige to the ^^ical ones 3ophysis) rhe faces upwards and inwards; those of the posterior downwards and out- wards. They articulate and form joints with processes •bf contiguous vertebrte. The transverse proceSvSes (diapophysis) on each side spring from the sides of the body and pedicle and vary in size and shape in different regions. The spinous processes are superior and inferior; the superior being larger and of different size in different regions; the inferior are rudimentary except in the cervical region. The bodies of the vertebrae placed in natural apposi- tion thus form a central bony column, to which the arches and processes are attached. The arches, with ^ their connecting ligaments, form superiorly a cavity, the spinal or neural canal, which extends from the head ' to the tail and contains the spinal cord with its mem- branes and blood vessels. The articular processes strengthen the connections, while the spinous and transverse processes are levers to which muscles are attached, their development having great influence on the physical conformation and capabilities of the ani- mal. The ribs may be considered as continuations of the dorsal transverse processes. They form the inferior or haemal arch of their own region. False Vertebrae. The false vertebrae are found in the sacrum, w^hich consists of vertebral segments united by the ossifica- tion of their connecting material; and in the coccyx, the skeleton of which consists of rudimentary or im- perfectly developed vertebrae. The sacral segments in the early stages of life are separable and present all the characteristics of true vertebrae. Cervical Vertebrae. General Features. There are seven cervical verte- brae in nearly all mammalia. They are numbered in order from the head ; the first is called the atlas and the second the axis or vertebrae dentata; these, wnththe 6th and 7th differ from the rest, which are essentially alilie. The bodies of the cervical vertebrae are larger and longer than those of any other true vertebrae, are quad- rangular in shape. The anterior surface or head is con- —IS— ri i III Mi i vex and vsomewhat heart shaped with the apex down- wards, while the posterior surface presents a corres- ])on(ling cavity. The s iperior surface is flattened, and presents, close to the pedicle on each side a distinct fur- row which contains the spinal vein ; these lateral furrows are united by a transverse furrow and partly covered by a thin, l>ony plate. The inferior surface possess a spin- ous ])rocess which increases in sixe from before back- wards, terminating in a tuberosity.* The lateral surfaces of the body above the inferior spine are flattened and somewhat excavated. The superior spinous processes or neural spines are mostly rudimentary and are bifid posteriorly. The transverse pr.)cesses are broad, short, strong and irregular in share, pass directly outwards and divide into two parts. All of them except the 7th are pierced by the vertebral foramen for the passage of the vertebral artery and vein. The aiticular processes, larger than in any other region, have flattened, oval, articular surfaces, the anterior two looking upwards and inwards, the posterior downwards and outwards. The 1st, 2nd, 6tli and 7tli having peculiar confirma- tion require special notice. T/w Atlas (as the first is called) because in human anatomy it supports the head; in quadrupeds the head is supported from it, presents no well defined body, but consists of a strong ridge of bone, the superior surface convex with a slight longitudinal elevation in the median line from which the wings slope dowmwards and backwards. The wings are large, flat transverse processes wider than those of any other true vertebra, each is pierced superiorly by three foramina, two anter- iorly and one posteriorly. The anterior surface pre- sents two notches and two large concave articular facets for articulation with the condyles of the occipital bone. The posterior surface is excavated on its inferior margin to receive the odon oid process of the axis, and on each side is a broad, slightly convex articular surface. The atlas is the only vertebra possessing none but true joints. The Axis or vertebra dentata possesses a larger body than any other true vertebra and anteriorly presents a peculiar projection called the odontoid process which fits into the ring of the atlas and around which the head and atlas rotate. The superior spine is nearly as toi ha an sn piJ eni Iv abl th »tj pel tr masBk \ \ —19- e apex clown - Its a corres- flattciied, and a (listinctfur- atera] fnrrows ^• covered b) >«sess a spin- before back- tera] snrfaces flattened and 3US processes and are bifid ^road, sJiort, tly outwards cept the 7th e passage of ir processes, ttened, oval, "R upwards outwards. if confirnia- in human fls the head t\body, but , nor surface ion in the downwards ^ t transverse le vertebra, two anter- u I face pre- cular facets e occipital its inferior the axis, X articular ssingnone irger body presents a -ss which which the nearly as loiij; as the body, is convex and consists of two lateral halves united anteriorly. The inferior spine is sharp and well developed. The transverse ])rocesses are the smallest in the cervical region anm m' i ji -2..- roccsses, a re I The ex- ?tween the lar attach- 'om above is smooth, ception of fib has its Icartilage. Those attached to the sternum are smallest ^t their proximal ends, becoming expanded before at- Itachment to the sternum, while those of the false ribs %rti largest at the proximal ends, tapering to points i)elow, pass downwards and forwards overlapping each other. Each true rib has 4 articular surfaces, two on the head, one on the tubercle and one at the distal end. Sternum. The sternum, or breast bone, is placed in the inferior longitudinal line of the body at the antero inferior part of the thorax. The anterior portion somewhat re- seml)ies the keel and cut water of a boat; it is elongat- ed and concave above, convex below, with its anterior part flattened laterally and its posterior part flattened above and below. It is constructed of six or seven irregularly formed segments or stern ebrae, united by cartJage in the young and by partial ossification in the adult animal, (complete ossification seldom or never takes place in this bone) . Its anterior end is surmount- ed by the cariniform cartilage and its posterior ex- tremity prolonged by the ensiform or xiphoid cartilage. The superior surface is triangular and concave, the in- ferior surface is narrow and convex anteriorly, the cen- tre presents a prominent ridge coated with cartilage. The sides are flat and irregular and present between the segments depressions for articulation with the costal cartilages. The cariniform cartilage presents a convex border looking forwards and upwards; latterly it is flattened, and its inferior border, prolonged over the first segments of the sternum, ends in the cartilaginous ridge. The ensiform cartilage is somewhat heart shaped, the apex being directed downwards and backwards. Its super- ior surface is broad and cup- shaped, its inferior surface is convex. The bony frame work of the thoracic cavity bears some resemblance to a truncated cone with its apex or anterior extremity compressed laterally. The anterior aperture is a triangular space, with its apex directed downwards and slightly forwards, formed by the ster- num, the first pair of ribs and the first dorsal vertebra; it gives passage to the oesophagus, trachea, nerves and —24- I '- { liliii! I I blood vesselvS. The base or posterior aperture is ova! and slopes obliquely downwards and forwards from the vertebrae; it is formed by the last dorsal vertebra, the last pair of ribs, the cartilages of the false ribs and the ensiform cartilage. Its boundaries give attachment to the diaphragm, a large muscular curtain which divides the thorax from the abdomen. The Skull. General View. The skull articulates with the atlas from which it is .suspended. Its position varies with the attitude of the animal but in our descriptions we shall always .suppose it to be placed in a horizontal po- sition. In the young animal it is composed of a num- ber of bones, all of which, wnth the exception of the lower jaw, the teeth, the bones of the tongue and ossi- cles of the ear unite by ossification in the adult. Ex- cluding the teeth and the internal bones of the ear there are 36 bones in the skull, 6 single, the rest in pairs. The skull is divisable into two parts, the cranium and the face. The former is a cavity situated in the supero posterior region of the skull and continuous with the spinal canal, it contains the brain and its appendages and in the horse is comparatively small, occupying about one -fifth of the skull. The remaining bones form the face. In early life the bones of the head are united by sutures, or interj^osed layers of fibrous tissue, and after union by ossification a line usually indicates the position of the late suture. One of the principle sutures is the longitudinal which extends in the median line from the poll to the nasal peak, and marks the division of the skull into two lateral halves. In describing the skull we will suppose it placed in a horizontal position resting on the lower jaw and divided into superior, inferior, lateral, anterior and posterior regions. The superior region is a surface formed by 3 pairs of bones, the parietal, frontal, and nasal, each bone being joined to its fellow by a part of the longitudinal suture. The parietal bones are the hindermost of the three, are .convex, and form part of the roof of the cranium or brain cavity, the frontal pair are flatter and very broad i ail i m ti c| 'V t .srous tissue, ly indicates he principle the median 1 marks the placed in a ind divided 1 posterior ^ pairs of 3one being II al suture. three, are -ranium or ^ery broad % )Ove the level of the orbits, the region of the fore- liead. The nasal bones together form a semi -cylinder, ind gradually diminish in breadth anteriorly, forming |lie nasal beak. The prominent transverse ridge ii)ounding this region posteriorly is the occipital crest. The inferior region presents a very irregular surface, bounded below by the inferior maxilla or lower jaw, a bone whose two segments are firmly united anteriorly, but diverge backwards in the form of a letter '*V" each terminating superiorly in a convex articular surface, the maxillary condyle, before which is the prominent coronoid process, the lever of the lower jaw. The di- *Verging parts or rami of the jaw include a space called the maxillary 'space. We find in the anterior portion the inferior incisor teeth, and in the male the canine teeth, and in the rami the inferior molars, the space between the molars and incisors is called the interdental space and is always large in herbivorous animals. If we remove the inferior maxilla we notice the following objects: Anteriorly, the premaxilla, bearing the upper incisors and partly the canine teeth, and just behind the incissors, in the median line, a small round aperture, the foramen incisivum, while the interdental space and molar teeth are similar to those in the lower jaw. The flattened surface extending from the incisors back- wards between the molars is the bony palate, formed chiefly by the superior maxilla, and bounded posterior- ly by the palatine arch, which is semi-eliptical in form and marks the entrance to a large cavity above called the nasal chamber; this cavity is, in the fresh state, divided into right and left compartments by a cartila- genous septum, the septum nasi. Between the posterior molars and the palatine arch are the two palatine foramina, behind, and bounded by the palatine arch are the entrances to the nasal cham- ber, right and left, called the posterior nares, and the slender median bone stretching from behind forward in the cavity is the vomer, which indicates the division of chamber into right and left fossae. Continuous with the vomer we find an irregular column of bone reach- ing to the back of the skull; this column consists of three pieces, the presphenoid anteriorly, then the basi sphenoid and lastly the basi occipital. On the poster- ior edges of the palatine arch are two small sharp pro- -26— 1 ' 1 I jectioiis, the ends of the pterygoid bones, and behinii them the rough palatine ridges, the posterior edges ot which are formed by the pterygoid processes of tht sphenoid bone, outside the base of each of these pro- cesses we have tlie posterior aperture of the subsphe- noidal foramen. Just behind the last molar teeth art two large prominences, the alveolar tuberosities, be- tween which, and the palatine ridges and pterygoid bones are the smooth staphyline grooves. Outside the palatine ridges are two large spaces, the orbito-tempo- ral cavities, each of which is bounded externall}- by the zygomatic arch, anteriorly by the alveolar tul)erosity. posteriorly by the articular surface of the squamosal bone, with which the inferior maxilla articulates, and internally by the sphenoid and palatine bones. Each cavity opens by two large apertures on the lateral avSpect of the skull, the posterior portion is called the temporal and the anterior tlie orbital fossa. The articular surface of the squamosal bone termi- nates posteriorly in a projection called the anterior mastoid process, behind and internal to which is an irregularly shaped bone, the petrosal, which contains the internal mechanism of the ear and gives attach- ment to the bones of the tongue (the os hyoides). Be- tween the petrosal and the basi occipital w^e have a large aperture leading into the cranial cavity, the for- amen lacerum basis cranii. Posterior to the petrosal bones are seen two large processes pointing downwards, the styloid processes of tlie occipital bone, (these must be distinguished from the small petrosal bones). Still further Ijack we have the occipital condyles by which the head articulates with the atlas. The lateral surfaces exhibits inferiorly the external surface of the rami of the lower jaw, and antero- super- iorly a triangular space, formed chiefly by the superior maxilla, more or less convex but sometimes hollowed in old animals, and presenting the infra-orbital fora- men in its centre. The zygomatic arch presents exter- nally a well marked ridge or line, which is continued anteriorly by a ridge called the maxillary spine. A process throw^n outwards and downwards by the fron- tal bone articulates w^th the zygomatic arch about its middle ; it is called the frontal or external orbital arch and it indicates the division of the cavity within into tl 3 'Ki»imfWt\ l.iM*»*a<.'*l*tW«'.-' —27— >tenor edges of ^rocesses of the »J of tJiese pro- f the subsphe- "olar teeth an i^erosities, be- and pterygoi,! Outside the orbito-tempo- snial] y by the ar tuberosity J|e squamosal ticulates, and hues. £;ach '. tile lateral IS called the bone termi- t^^^ anterior I which is an iich contains r- In the ane. J the bones •s and those The horse, ' of legs, an posterior, connection, rches. In > no articu- the trunk, Scapula. The scapula is a fiat bone situated on the antero- lat- eral surface of the thorax with its long axis sloping own wards and forwards. It is triangular with the ase turned upwards. (In the horse this bone is small ut strong, it is broad and thin superiorly, becoming piarrow and thicker inferiorly. Its slope is a point of |importance in the conformation of an animal, and varies o some extent, but its inferior angle is situated about he level of the first rib, the posterior angle being sually at or near the level of the 6th or 7th.) It offers for consideration 2 surfaces, 3 borders and J 3 angles. || The external or dorsum svirface is divided into two ^unequal parts by a crest called the spine running near- fly the whole length, and has a tubercle at its broadest part. (The clavicle, in animals that possess one, is attached to the inferior extremity of the spine.) The hollow part in front of the spine, the antea spinatus fossa receives a muscle of the same name. The postea spinatus fossa (behind the spine) is larger, and receives the postea spinatus muscle. The nutrient foramen is in this fossa. T/i(7 internal or ventor surface is smooth and uneven, its fossa, the subscapularis, lodges the subscapularis muscle. -30— - The superior border is nearly straight and has tlu cartilage of prolongation attached to it. The anterior border snperiorly is convex and sliarj!, inferiorly concave and blnnt, terminates in the coracoi' apophysis for muscular attachment. The posterior border is blunt and rough. The anterior angle is thin, the posterior thick. TIk inferior expanded, and vSeparated from the rest of tlu bone by a neck, and contains an articular depression, the glenoid cavity, articulating with the humerus, and surmounted by a roughened ridge for insertion of tht capsular ligament. Humerus. CI si 1 The humerus is a long bone extending obliquel> downwards and backwards from the scapula to thc radius. It possesses a shaft and two extremities. The shaft is twisted, with 4 surfaces. The anterior surface is somewhat triangular with the apex down- waxds. The posterior is round and smooth and termi- nates inferiorly in two prominent ridges, the epitroch- lea and epicondyle. The external surface contains thf musculo spiral groove which wnnds obliquel}^ down- wards and forwards and is separated from the anterior surface by the deltoid ridge, which extends from the proximal end to the coronoid fossa. A rounded promi- nence, the external tuberosity is seen on the upper part of this ridge bending backwards over the spiral groove. The internal surface has no distinct separation from the anterior and posterior surfaces ; it has a prominence, the internal tuberosity, about its middle third,. The proximal end presents the head and the troch- anters. The head is convex, and larger than the glen- oid cavity with which it articulates, allowing extensive and varied motion, it is surrounded by a roughened border for insertion of the capsular ligament, below which is the constticted neck of the bone. The external trochanter has two prominences, the anterior or summit of the trochanter, which forms the external boundary of the bicipital groove gives inser- tion to the outer tendon of the antea spinatus muscle, while the posterior, the more prominent of the two, is ■ tF'S-JW.^^aKBMfJ ■,VSK**»*r»i; —31- M and has tlu -ex and sharp, in the coracoi. rh. •r thick. Tht the rest of the lar depression, • humerus, and nsertion of th( li"g obliquelx papula to the emities. The anterior e apex down- th and ternii- the epitroch- con tains the iquel3' down- 1 the anterior nds from tlie nded promi- le upper part piral groove. ion from the prominence, rd„ the troch- an the glen- ig extensive roughened ttient, below nences, the h forms the gives inser- tus muscle, the two, is covered bv fibro cartilage over which glides the tendon the postea spinatus, which is inserted to a rough rface below. T/ie mternal irocfianter is divided into 3 parts, an- tirior. ])osterior and inferior; the anterior forms the internal boundary of the bicipital groove which is ^vided by a middle prominence into two channels 'W^hicli are covered with fi1)ro cartilage and serve as a fillev over which the tendon of the flexor brachi uscle plays. {; yiic distal extremity is smaller and smooth to arfc- tllate with the radius and ulna, its surface is convex and wider in front than behind. A groove, terminating in the olecranon fossa posteriorly, divides it into an internal and external condyle or trochlea, the latter being the smaller. The Forearm. The bones of the forearm are the radius and ulna, which in young animals are distinct, but in the adult become united by ossification and are sometimes de- scribed as one bone, the os antibrachii. We will de- scribe them separately. Radius. The radius is a long bone placed vertically between the humerus and the carpus. The shaft is flattened and curved with gradually expanding extremities. Its anterior surface is smooth, its posterior concave from above downwards, and presents, towards its external .^iborder, a rough triangular surface to which the ulna is ■^attached by interosseous ligaments in the young, and :^y ossification in the adult animal. The shallow, trans- verse groove above this surface assists in forming the jjadio ulnar arch, and the nutrient foramen is near this groove. The external and internal lateral surfaces are |round and have no distinct separation from the anterior md posterior surfaces. The proximal extremity is widest from side to side land presents ari articular surface divided into tw^o de- )ressions, the glenoid cavities, which receive the con- lyles of the humerus, the inner is the larger, the outer las a slight eminence in its centre, A rough ridge [around the surface gives attachment to the capsular -^32— ligament, the anterior part has a prominent lip, th.w corocoid process, in its centre, and near the inteniate border the bicipital tuberosity. On each side of the arw! ticular surface is a rough portion for the lateral liga th< nients, the external of which is called the external tubi tb rosity. Posteriorly two facets articulate with the ulna a The distal exlronity is also widest from side to side a its articular surface is divided into three facets; tlit internal, the largest, articulates with the scaphoi( bone, the middle with the lunar, the external, tlu smallest, with the cuneiform and trapezium. Tlu whole is surrounded by a ridge for the capsular liga nient. The anterior part has two deep vertical grooves and a shallow oblique one, laterally two processes, the internal the larger, for attachment of the lateral liga- ments. ei fo ai rina. The ulna is an irregular bone, triangular in form, with the base uppermost. It grows but little afterbirth, It possesses a body and two extremities. The body i^ triangular and has three surfaces and three borders. The anterior surface corresponds to the posterior sur- face of the radius to which it is attached, having super- iorly two convex facets to articulate with the radius; below this is a rough, portion for the attachment of the interosseous ligaments, and still lower a transverse groove wdiicli assists in forming the radio ulnar arch. The external surface is flattened, the lateral borders are thin, the posterior border concave and round, the distal extremity is pointed and extends a little below the middle of the radius. The proximal extremity corresponds to the elbow of man; it projects upwards and backwards from the artic- ular surface of the radius and is called the olecranon process. It presents two surfaces, two borders and a summit. The external surface is slightly convex and rough, and internal surface is hollow and smooth, the posterior border concave, thin and smooth; the anterior border, thin superiorly, is hollowed into a crescent shaped surface, which articulates wnth, or rather be- hind and between, the condyles of the humerus, the prominent portion is known as the beak of the olecra- non. The summit is the broad rough protuberance la si ai tr 01 tt zc tc ft b a t: c t t •-l«^i —33— icli j^ives insertion to the tendom of the triceps ex- [sor brachi muscle, the olecranon being the lever on icli that muscle acts. (It is important to note that development of the ulna is directly proportional to number of fingers or digits, hence the horse, being lonodactyle, has a very short ulna. While in the ox dog it is much longer.) »»nnent lip, tli.wl ear the internatc 1 side of the arw^ the lateral liga tl| e external tubitl e with the uhiaa. oni side to side aj iree facets; tli, f the scaphoif ^ Cai'pus. external, tin ■; ipezium. 'f ]], f}*]ie knee, or carpus corresponds to the wrist in man. capsular li^a Xjbere are seven bones in the knee and occasionally an ertical groove^ e||?hth is found which is very small and called the pisi- ' P^l^^esses, tile foffm ; with this the knee consists of eight bones, named he lateral liga- aiid arranged as follows in two rows: The scaphoid occupies the inner side of the upper layer, the lunar the centre and the cuneiform the outer side. The trapezoid the inner, the magnum the centre and the unciform the outer side of the lower row. The ttle after birtli trapezium is situated behind and articulates with the The body i> Ctmeiform, consequently it occupies the outer side of three borders, the knee, and the pisiform is found behind the trape- posterior sur- 2spid. These bones are all somewhat similar in charac- having super- ter; they are irregular in shape, and possess small ith the radius; fucets to articulate with each other and with other ichment of the bones. The upper row forms an articular surface a transverse adapted to that of the lower extremity of the radius, io ulnar arch, ^e inferior surface of the upper row presents a slight Concavity for articulation with the superior .surface of e lower row. The under surface of the lower row is early flat and articulates with the metacarpal bones. he true carpal joint or principal seat of motion is etween the radius and the upper row, there is less mo- ioii between the rows, and still less between the lower ow^ and the metacarpus. (The lesion, termed broken nees, usually occurs where there is the most extensive otion.) ?ular in form ■al borders are md, the distal >tle below the • the elbow of rom the artic- the olecranon borders and a y convex and I smooth, the ; the anterior o a crescent f rather be- fiumerus, the >f the olecra- protuberance Metacarpus. The metacarpus is that part of the skeleton which lies between the carpus and the finger, consisting in phe horse of three bones, one large one and two small mes, ealled splint bones. —34— ii Hi ■Hiill If Os Metacarpi Magfiinni. The lar^e nietacar])al, or canon bone is a loi straij^lit l)one, placed in a vertical direction, having flattened shaft; the anterior surface is convex an smooth and the posterior broad, flat and pierced ;i about the upi)er third by the nutrient foramen; on e;u, side of this suiface is a vertical ridge to which the spliii bones are attached. The proxi)nal cud presents a smooth articular sur face formed by three facets corrCvSponding to the lowe surface of the lower row of the carpus; on the inteio anterior ])ortion of the head is a prominence for tlit insertion of the extensor metacarpi magnus tendon On the posterior part is a rough surface from which llu suspensory and clieek ligaments originate, and on earl; side two facets to articulate with the splint bones. The distal cud is formed by two condyles, convtN from before backwards to articulate with the os suffra ginis below and the sesamoid bones behind; each con dyle presents a depression on its side for attachment o; the lateral ligament. * Os Metacarpi Parva. The small metacarpal, or splint bones are tuberous above and taper to a point below reaching about - ( down the large bone. The superior surface of each bone articulates with the carpus, the inner one has two facets and the external one but one; below the articular surfaces externally the heads are rough. The internal lateral parts of the heads each present two articular facets to articulate wnth the large metacarpal. The anterior surface is flat and attached to the posterior surface of the large bones, one on each side, by liga- ments in young animals and sometimes by ossification in the old. The bones gradually taper to a point or apex which terminates in a small knob. (These knobs are very prominent in well bred animals and are some- times mistaken for splints, which are exostosises be- tween the large and small bones.) Digfit. The digit or finger is composed of three bones j)lacecl one immediately below the other and having three —35- ni. .bone is a hu irection, liavin^ e is convex ai: It and pierced foramen ; on eaci o which the sp] in ►th articular siir tliJiK to the lowe s; on tlie intero ninence for tin ma^nus tendon ? from which llu ate, and on eacli hnt bones, ■ondyles, convex seiftnioid bones behind. The joint which tlie larije metae-arpal forms with the os suffraj^inis and its two seianioid hones is the fetlock joint, that between the 08 suffra;^ijiis and os cotoikl is the ])astern joint, and that between the os coron;e and the os ])edi^ with its sr attachment les are tuberous aching about -, surface of eacii er one has two 'W the articular The internal It two articular acarpal. The the posterior side, by liga- by ossification > a point or (These knobs ind are some- xostosises be- bones jjlaced laving three || Great Sesamoid Bones. ^ These bones, two in number, are placed side by side 1^ the back of the fetlock ; they are irrejjjidar in shape li|ith smooth and concave anterior surfaces with the * iternal edges bevelled to articulate with the ridge of le metacarpal bone. The posterior surfaces, when in Ituation, form a channel which is covered with fibro ii&rtilage for the passage of the flexor tendons. The kpnx and lateral borders are rough, and form a groove fr the reception of the suspensory ligament. The base also rough for ligamentous attachment. Os Coroiiae. The OS coronae is an irregular bone, with no madul- ry canal. The superior surface is smooth, and divided an eminence into two glenoid cavities for the con- yles of the os suffraginis. The inferior .surface is ooth and convex, and divided by a depression into o condyles which articulate with the os pedis and os iiaviculare. The anterior surface is convex and very ilough. The posterior surface is slightly excavated and mm 4i -36— Os Pedis. thecals or wings. '"'^f«<^«. "'e articular surface a ' Part1„"Tro;,ra,:d'p1::e„T;';r'^' '■'' *^ -mi-circuh. pet' sr i,r'"^'( '^"- Suo^fo ^.i;"'^^-"- ulaSs with "/l"'" Pyr«'"idalVrocess^ H.f""'";"'^^ «'hi<--'i Os iVavicular. ■T^^ie navicular ' —37- Partan emiiicn, ^ P^ays the teiKi,, ^ated within th the convexity i le, having nran- iiission of arte ice the wall, tli, iJar surface an, e semi-circula- repressions an, -« by the pyra- to the extensor side of whicli re of the wall :\ tlie preplantar en of the sam. slightly exca- > surface is tli, ;S a triangular •or part, where »s is inserted, ich terminates ft of this sur- presents two iinence whicli surface artic- vities, a flat, the OS navi- ances on the •eing divided old animals and poster- ess, and the ted with its - OS coronse ^ it articu- tes forming the so-called coffin joint. The superior •face is smooth, with two concavities and a central iinence. The inferior surface is rather rough and is also two concavities and a central eminence cuv- id with fibro cartilage which forms a pulley over licli plays the tendon of the flexor perforans. The Iterior border is divided into two portions, a superior, looth and Liiangular which articulates with the os idis, and an inferior elongated, rough and porous, le posterior border is triangular, rough and porous. he extremities are pointed and attached to the alae of le OS pedis by lateral ligaments. Pelvic Arch. :§ The posterior extremity is united to the trunk b}' the 'direct articulation of the pelvic arch with the femur and sacral vertebra. The three bones which form the arch unite early by ossification and the entire arch is ^Jailed the os innominatum. The two ossa innominata ijiirticulate with each other in the inferior median line, and at a later period this union also becomes ossified; |he complete structure is called the pelvis, and the Space which it helps to enclose is the pelvic cavity, which is the incomplete basin composed of the sacrum, |)art of the coccyx and the two ossa innominata, each of §vhich is composed of three bones, viz. : the Ilium, ischium and Pubis, which all meet in the acetabulum, or articular cavity for the femur. Ilium. The ilium is a flat bone situated partly upon the sac- rum with which it articulates; it is irregularly triangu- lar in shape, its extreme outer angle being one of the most prominent points of the animal, forming the point of the hip. It presents for consideration two surfaces, three borders, and three angles or processes. T/ie external surface is concave at its upper part, be- coming convex and narrow further down, forming the :upper part of the shaft of the ilium ; as it approaches the acetabulum the shaft again slightly expands. This surface terminates in an obtuse angle, the outer side of which forms the anterior margin of the acetabulum ; and the inner side, surmounting this cavity, marks the line of junction between the ilium and the ischium. ii i 11 Ir' ' It —38— The internal surface is slightly convex, its uppei portion consists of two parts, an outer smooth one, and an inner rough one which rests on the sacrum ; on tlit lower portion is a line continuous with the brim of tlu pubis. Together these form the ileo pectineal line. The anterior border, or crest of the ilium, lies abovt the sacral transverse process. It is concave above, con- vex below and thin in the middle. Internally it ter- minates in the posterior iliac spine, which forms the highest part of the hips. Kxt ^illy and anteriorly it terminates in the anterior ili pine which consivSts of four eminences, two superior a.-d two inferior. Thtv are more developed in some horses than in others and sometimes project so far as to form what is calltil ''ragged hips." The stiperior or internal border extends from the posterior spine to the ischium. It is sharp and thin above, becoming thicker posteriorly, presenting abovt the acetabulum the sciatic or superior ischiatic spine The external border extends from the anterior spine tci the acetabulum, and is concave, blunt and rough. Ischium. 'I Mi The ischium, smaller than the ilium, is a flat bone, irregularly quadrilateral, which extends from theacet^ abulum, and forms the posterior part of the pelvis. It presents a body, shaft and ramus. The shaft joins the ilium at the acetabulum, it is rounded and forms the external boundary of the obtur- ator foramen. The body is nearly horizontal, flat, smooth, and forms the posterior boundary of the olDturator foramen. In- ternally it is rough and joins its fellow of the opposite- side forming the symphysis ischii. Posteriorly it pre- sents a prominent projection, the tuberosity of the ischium. The ridge running forward from the tuber- osity is the inferior ischiatic spine. The posterior bor- der is thick, running from the tuberosity to the sym- physis, forming with its fellow the ischial arch. The ramus, not well developed in the horse, is the small branch which joins the pubis and forms part of the in- terior boundary of the foramen orale. :onvex, its uppe: smooth one, and e sacrum ; on tlit !i the brim of the ^ctineal line, ilium, lies above cave above, con- iternally it ter- which forms the and anteriorly it t^hich consists of inferior. They in in others and what is called ends from the < sharp and thin resenting above ischiatic spine, nterior spine to id rough. a flat bone, from theacet he pelvis. it tabulum, it is y of the obtur- )th, and forms )ramen. in- f the opposite ^riorly it pre- rosity of the mi the tuber- 'osterior bor- ^ to the sym- arch. The is the small art of the in- -39- Piibis. The pubis is the smallest bone of the os innominatum. It is irregular in shape and forms with its fellow the a^tero inferior part of the pelvis. It consists of a body sdsid a ramus. 77/^ dody reaches from the acetabulum to the median symphysis. Its superior surface is concave to receive the urinary bladder, its inferior convex and crossed by a^^^ groove from the acetabulum which contains the piibio- femoral ligament. The crest is the rough anter- ior border, which terminates in the symphysis. The Upsterior border extends to the ramus and forms the ainterior margin of the obturator foramen. The outer eiftrernity, which joins the ilium and ischium in the <||cetabulum is excavated to form the colyloid notch. ^e ramus is the flattened portion which extends pos- leriorly, joins the ramus of the ischium, forming part (jlf the boundary of the obturator foramen and with its jfl^liow the symphysis bubis internally. ■■■•* ■1 Acetabulum. The acetabulum, situated on the extero-lateral aspect i0f the pelvis is formed by the three segments of the os fenominatum. It receives the head of the thigh bone §nd is one of the deepest articular depressions in the ly. It is circular in outline and except at its infer- )r- median part is surrounded by a lip of bone. Its ferior border presents a large notch, the cotyloid ilotch, continued half way across the articulation as the fundus acetabuli, to give attachment to the round ligament. ^ Obturator Foramen or Foramen Ovale ^s the largest foramen in the body, exivSts in each os in- tiominata and is formed entirely by the ischium and pubis. g Pelvic or Posterior Extremity. p The bones of the hind limb are the femur, tibia, pa- tella and fibula; the bones of the tarsus, viz., the astra- Igalus, OS calcis, one cuboid and three cuneiform bones; one large and two small metatarsals, three phalanges and three sesamoids. ,.:40 -40— M I Femur. The femur or thigh bone is the largest, thickest aiKi strongest bone in the body, belongs to the class of loiii; bones, is placed in a direction obliquely downward^ and forwards, articulating with the acetabulum and als( with the tibia and patella. The shaft has two surfact;- and two borders. The anterior surface is smooth, tht posterior flat and expanded at its upper part and pre- sents towards the external part of its upper third a circular roughened surface for the insertion of part oi the triceps abductor muscle. The external border pre- sents a prominent ridge, on the upper third of which is a protuberance, the trochanter minor, curved forwards At the low^er third of this border is a deep pit, the supra-condyloid fossa, and about level with this, towards the inner side, is an aggregation of tubercles forming the supra-condyloid crest. The internal border presents near its upper third the trochanter internus, from which another ridge runs downwards, in the lower part of which is the nutrieiit foramen. The proximal end terminates in the head and the trochanter major. The head is the articular surface directed forwards and inwards and is received in the colyloid cavity. It is separated from the shaft by the neck, and between the two is a roughened ridge for the attachment of the capsular ligament. There is a dee]) notch at the inner part of the head for the attachment of the pubio-femoral and round ligaments. The trochanter major is u large eminence projectinj^ upwards and outwards, the sunmiit of which stands a little higher than the articular head. Behind the tro- chanter is the digital or trochanteric fossa. The distal end presents posteriorly two condyles and anteriorly a trochlea. The condyles articulate with the head of the tibia and are separated by an intercondyloid groove, the external condyle has two foss£e on the out- side, the internal condyle has a prominence on its lat- eral surface. The trochlea is the pully shaped part to the front of the condyles which articulates with the patella. It consists of two prominences separated by a groove. -41- est, thickest and he class of loii. uely downward^ abulum and alsi lias two surf acts e is smooth, tlit -r part and p re- ts upper third a ^rtion of part of nal border pre- lird of which is irved forwards, a deep pit, t!ie ';el with this, ion of tubercles upper third the ler ridge runs is the nutrient e head and tlie rticular surfaof received in the !ie shaft by the d ridge for the • lere is a deep he attachment s. ;nce projectini,^ vhich stands a 'hind the tro- i. condyles and Lilate with the ntercondyloid ^ on the out- -e on its lat-^ o the front of i patella. It i groove. Patella. 'his, the knee-pan or stifle bone, is placed in front ol the trochlea of the femur. Its anterior surface is CgOnvex and rough, its posterior surface smooth to artic- lii|iate with the femur, presenting two concavities divided w^ a ridge, the superior surface is broad, the inferior TOrface rough and pointed. Tibia. The tibia, or leg bone slants downwards and back- wards between the femur and astragalus. The shaft ii three sided, presenting outer, inner and posterior surfaces, all of which are wider above than below. The <|uter surface is concave above and convex below and fmooth. The inner surface, slightly convex from side 1^ side, is smooth except at its superior part. It is Covered chiefly by .skin, facia, and strong periosteum. The posterior surface, the broadest of the three, pre- sents on its upper third a triangular and rather smooth portion, the other two -thirds being marked by a num- ber of longitudinal ridges. The proximal end presents two large, smooth, some- what undulated articular surfaces, divided b\- a rough conical process, the tibial s])ine. The semi-lunar car- tilages are interposed between these surfaces and the condyles of the femur. Anteriorly a tuberosity, con- Cave externally and convex internally joins the tibial tidge, and presents a vertical notch in front for the middle straight ligament of the patella. At the sides are two processes to which the lateral ligaments are at- tached, the external being the larger and presents an articular facet for the head of the fil^ula. The distal end presents two smooth, deep articular grooves, running obliqueW backwards and inwards, the internal being the deepest, the external the widest. Also three projections, the middle one dividing the grooves, is articular and continuous with them, while the others are rough outside for attachment of liga- ments. Fibula. The fibula is a long slender bone, little developed in the horse, and is an appendage to the tibia, being at- tached to its outer side and extending from its head to -42— 'mi. ■ I Its lower third to which it is affixed by a ligament,, tlit space between the bones is called the tibial arch. Tin head is nodular, flat and rough externally. Internally it articulates with the external lateral part of the htar of the tibia. Distally the bone becomes slender an* tapers to a point from which a ligament is sometime; continued the whole length of the bone. Tarsus. T*ie ; . sus, or hock, corresponds to the ankle of man, and is composed of six irregular bones placed betweei the lower end of the tibia and the superior extremit of the metatarsus. They are arranged in two series one consisting of the cuboid and three cuneiform bones, the majrr"'^^ rriedium and parvum, corresponds to tlu lower t'jw f>i ^ he jarpal bones, the other or upper series, consists cf t ,c iistragalus and calcaneum, the first forming with tht b^ne above the mobile portion of tht joiuc, ma_v be sai<: 'o correspond to the upper row o; carpal bones, Aih"^ ;h-^ latter, being the lever bone, corresponds to the trnptAiam. These bones are thickh covered on their articular surface by cartilage, which acts as a protection against concussion. Astragalus. The astragalus or ankle bone is a pully-like bont placed immediately below the tibia with which it artic- ulates. (A very large portion of this bone is articular. The supero-anterior surface presents an articular trochlea consisting of two oblique prominences separat- ed by a groove. The inferior surface is concavo-con- vex. The posterior surface is very irregular and has four facets. The lateral surfaces, the internal of which presents a tubercle inferiorly, are roughened for the insertion of ligaments. (The astragalus articulates with the tibia, calcaneum, the cuboid and great cunei- form bones) . Calcaneum. The OS calcis or calcaneum forms the point of the hock and corresponds to the heel bone of man, is situ- ated behind the astragalus snd consists of a body and a tuberosity. The body is the inferior portion flattened laterally, slightly convex externally and unevenly con- M a ligament, tin )ial arch. Tlit ly. Internalh part of the hear tnes slender am it is sometimes e ankle of man, placed between )erior extremit} d in two series jneiform bones, esponds to the or upper series sum, the first portion of tht le upper row o: he lever bone, lies are thickh [artilage, which ully-like bone which it artic- le is articular, i an articular lences separat i concavo-con- sgular and has Jrnal of which hened for the us articulates d great cunei- e point of the man, is sitii- a body and a tion flattened nevenly con- -43- cave internally, both surfaces beinj^ rou^h. Anteriorly it;^;lias four articular facets to articulate with the as- tragalus. Posteriorly it is convex anil smooth, liifer- iojrly it has two facets to articulate with the cuboid- trtfce tuberosit}' is oblong and flattened laterally, its ex- tjfernai surface is rough, internally it is smooth and iocxas the tarsul arch, covered with fibro cartilage. Both borders are rough, the posterior one straight and gives attachment to the calcaneo-cuboid ligament, the anterior border is short and curved. ^he superior extremity is expanded and rouglienetl. I^steriorly it is covered witli fibro cartilage for the |!iBsage of the gastrocnemius internus tendon. Anter- ll^ly a small portion is also covered with fibro cartilage |(|r the gastrocnemius externus. * Os Cuboides. The cuboid is a small irregularly shapeil bone which occupies the outer side of the hock between the os cal- cis and the large and outer small metatarsal bones. It isresents four surfaces. Os Cuneiform Mag-num. The large cuneiform is the bone on which the astra- galus rests. It is somewhat flat and thin and presents WO surfaces and a circumferent border. Os Cuneiform Medium. The cuneiform medium is somewhat flat and triang- i!|lar and a little smaller than the magnum under which it is placed, articulating inferiorly with the large meta- tarsal. Os Cuneiform Parum. This is a very irregular bone, the smallest in the liock, at the postero-internal part of which it is placed. It articulates with the large and medium cuneiform bones and with the large and internal small metatarsal bones. Metatarsal Bones. The large metatarsal bone presents the same general appearance as the large metacarpal, but is about one- aixth longer, flattened laterally, and rounded, and —44- ini^li' more prominent anteriorly. The inferior extremity larger and thicker than the superior. The small niela-t tarsals also resemble the small metacarpals but art longer and larger, the external being the longest. .^ The remaining bones of the hind extremity so clostly^ resemble those of the fore, that no description is necos sary except to mention that the first and phalanges are a little longer. Comparative Osteology. secoiKi g^ ol ?S 111 We will now mention some of the chief differences the bones of the horse and the ox. In the cranium of the ox an important feature is the development of the frontal bone, which extends from ])elow the eyes to the back of the skull, forming tlu entire forehead and crest, in the middle of which is llie frontal tuberosity, which is very large in hornless ani- mals. Springing from the sides of the crest are t\vo processes, varying in size and curvature, but corres- ponding to the shape of the horns wdiicli they support, These are the flints or horn cores which are porous in their structure, especially at their roots. They arc covered with thick periosteum, and contain sinuses which are continuous with the frontal sinuses. The parietal bone is placed below the frontal crest extending under and supporting the cores. The occipital bone is single, wnder from side to side, but smaller than in the horse, and has neither crest nor tuberosities. The squamosal and petrosal bones are united into a single temperal bone. The nasal bones are shorter and broader. The superior maxilla is shorter and broader. The premaxilla is shorter and broader, its inferior surface is flat and destitute of aveolar cavities. The inferior maxilla is longer but less massive, the neck more constricted, and the symphysis seldom be- comes completely ossified. There are eight small alveoli in front for the incisors and canines, the latter being close to the former. The true vertebral column is made up of 26 segments. 7 cervical, 13 dorsal and 6 lumbar. The bodies of the cervical are shorter than those of the horse ; the dorsal longer; the sacrum is large and more arched; the tl h 11 d a i< s i t -45— -lor extreniit\ . 'lie small meta- carpals but are e longest. ;mity so closelv iption is neces. Nt and second f differences 111 It feature is tlie 1 extends from II, forming tlu- >f which is the 1 hornless ani- e crest are two fe, but corres- ^ they supporl, I are porous in s. They are Mitain sinuses uses, e frontal crest |i side to side, ither crest nor ■ united into a der. ■r, its inferior ties. massive, the is seldom be- eight small es, the latter 26 segments, >odies of the ; the dorsal arched; the coccygeal, 13 to 20 in number, are stronger and more tuberous. The ox has 13 pairs of ribs, 8 true and 5 false. Tliey are straight, broad and long, and more uniform than in the horse. The distal ends are expanded to articulate with their cartilages bv means of true joints. The sternum is large and flat, consisting of seven pieces, all of which unite by ossification exce]U the first and sec- ond, between which there is a true joint. The OS innominatum is larger but presents the same general apperance as in the horse. The femur is distinguished from that of the horse by the trochanter minor being missing. The head is small hut prominent ; the trochanter major has l)Ut one emi- nence. The tibia has no articular facet for the fibula and the distal end has its external mallealus detached, forming a small bone called the malleolar l)one. The fibula is wanting, being replaced by a ligament stretching the whole length of the bone. The patella is small and somewhat conical in shape. The tarsus consists of five bones. The astragalus is deep but narrow, having a pulley shaped surface infer- iorly as well as superiorly. The calcaneum*is long and square. The cuneiform magnum and cuboid are united forming the cubo-cuneiform bone; the medium is like that of the horse, while the parvium is very small. The large metatarsal has its inferior extremitv divided into two equal parts by a deep fissure with a groove superiorly. The small metatarsals, when present, are rudimentary and single. m The scapula is large and very triangular. The spine does not terminate gradually in the neck, but by an abrupt angle, prolonged to a point, the acromion pro- 0BSS ; the neck is more distinct and the coracoid process and glenoid cavity are small and close together. In the humerus the bicipital groove is single, the ex- ternal trochanter very large and the shaft is less twist- ed than in the horse. The radius is short, the ulna longer and larger, ex- tending to the distal end of the radius and articulating with the cuneiform bone. There are two radio-ulnar «rches connected by a deep Assure. —46- The carpus consists of six bones, four above and u below. The large metacarpal presents a vertical groove dow its anterior middle. The inferior extremity is divided by a deep fissm into two articulations, each resembling the single or in the horse, the external one being the smaller, rudimentary metacarpus is placed postero-superiorly. The phalanges and sesamoids in either limb ai double, one set forming each digit; they are small ai; narrow. The coflfln bone or os pedis resembling half i that of the horse mesially divided. In the adult ruminant two bones are commonly foui. in the heart called the cardiac bones or ossa cordi- The}' are found related with the auriculo-ventricula rings. They present 3 angles, 3 borders and 2 sur faces, the left being considerably the smaller. Arthrolog-y. The several bones which form the skeleton are unite by means of certain soft structures, forming a series ( articulation or joints, the study of which is called artli rology or Syndesmology. Before considering the different kinds of joints \vt will briefly describe the various tissues, other thai bone, which enter into, and contribute towards tliei- formation. These are chiefly cartilage, connective am elastic tissues, and fat. In health one bone never comes directly in contact with another, cartilage or fibrous tissue being always interposed. An exception to this exists in the adult skull, most of the bones of which become firmly united by ossification of the interposed soft material. Cartilagfe. Cartilage, known also as gristle, is a firm, bluish- white, elastic animal substance, flexible and possessing great cohesive power. That which becomes converted into bone is called temporary, and that which persists as cartilage in the adult, permanent cartilage, and it never, under any circumstances, ossifies. Cartilage consists of corpuscles or cells, usually em- bedded in an intercellular substance or matrix. These cells are oval or round, and nucleated, the nuclei, which ►ur above and h ■tJcal groove do^ y a deep fissur ing the single or { the smaller, ero- superiorly, either limb ar ey are small an esembling half, commonly foun es or ossa cor(li> riculo-ventricula "ders and 2 sur mailer. eleton are unites tning a series o h is called artli nds of joints m ^es, other thai te towards tliei- connective am 'ectly in contact ue being alwavs ists in the adult le firmly united terial. a firm, bluish- and possessing omes converted which persists artilage, and it 3, usually eni- latrix. These i nuclei, which -47— appear imder the microscope as vSmall spots, containing still smaller st)ots called nucleoli. There are three varieties of permanent cartilage, viz., hyaline, fibro and cellular. In the first the matrix is homogeneous, or void of definite structure, appearing slightly granular under the microscope. Fibro-carti- lage is cliaracterized by a matrix of fibrous tissue, while cellular cartilage consists of an aggregation of cells without a matrix. Hyaline cartilage is distinguished by the following names according to the purpose it serves: Articular, when it encrusts the articular surfaces of bones; Costal, when it supplies elastic prolongations to the ribs; Membraniforni, when it appears as thin plates, forming permanently open tubes. (The trachea or wind pipe is formed of this kind). Articular cartilage in the adult is nonvascular, being nourished by a vascular zone in the synovial membrane. Fibro -cartilage consists of cartilage cells and fibrous tissues, which may be white or yellow, the former being tough and strong and the latter highly elastic. White fibro-cartilage is much the more abundant and presents the following varieties: It is called inter-articular when it appears as a pad interposed between the two articular surfaces which form a joint. Such a pad is termed a meniscus. The temporo-maxillary and fem~ oro-tibial joints are furnished with such. Circumfer- ential, where it surrounds and deepens an articular cavity, as the acetabulum. Connecting, where it is interposed between bones, firmly connecting them, as Between the vertebral centra. Stratiform, or investing, #hen it clothes the parts of bones over which the ten- ^clons of muscles play. (Yellow elastic fibro-cartilage li found in the epiglottis, in the framework of the ear, and the Eustachian tubes. Cellular cartilage is found in the ear of .some rodents and in the bat.) ?: Connective tissue, in one form or another, is found ifel all parts of the body. The chief varieties are the lireolar and the fibrous, the former serving as a con- medium and support to the various organs, the structures of which they are formed. It as a loose translucent mesh, its interwoven forming spaces termed the areolae or cells, md to i^pears l&undles H a —48— an 1 wans, are also pres.iu "' ""^"' ^^"'^'-''-s, "Uc mellow elastic fi - •■" pdiii. by heinK yellow. Z^^f^n^r'^^'' "'""^ "'-o '•■aterial, and arran^Ld ^, °^ ^"^""^ containing a„ „, oc^^x's^. j« '™i^ ^^'i-;' I^ig'aments. I^igaments are denc^ ^i sr"i,"? r"*~~. .*';»?;"*'* "t ■ f .'sri tr=' "".s ,'?s!&= "■* ""• '•- .~E°.gi» ™^^^^^ s= :/% .'j^ —49- '«f"^^- It cons, ^i] with small III. leir remains, uxu ostly paraJIcl a •ears in two forir found in invest! ^c., and the con -ted in strong l,i, dons. Connect • vessels. W],, ' the white fil,r„ tough and str.Mi ler and their e,i tound in the li^ ontaining an oi; groups or sh'oht It is found -atly in quantit' 'ts, and serves rm of marrow 'Cting structure >nncipally niad two kinds, viz "IK- Capsula enclosing tm nts consist f fibrous tissue 'Illy attached f, lyiganieut; termed inter hich bind dowr certain joints irely of yellov, chae.) Synovial MonihraneH. These are thin nitnibranes lining the ca])sular liga- ments of joints, or they are interposed between struc- tures wliicli move one ui)on another. They secrete a fluid, called synovia or joint oil, and they line closed Cf -s, rcsenililing what are called serous membranes. .*ere are three forms of these meml)ranes; the cap- sular, which line the ca]isular ligaments of the joints; bursal membranes, where one structure moves upon another (as where a tendon plays over a bone) and are known as synovial bursie; when they exist between the skin and certain ])rominent parts of the skeleton they are known as bursie mucOvSse. The third form, vaginal membranes or sheathes, exist where one tendon forms a sheath for another, or in other canals in which tendons glide. Synovia or joint oil is a viscid, trans- Earent fluid, colorless or pale yellow, resembling oil, ut it contains very little fatty matter, consisting liiefly of albumen, salts and water. When an animal is in a^ e exertion there is a greater demand for joint oil t vhen at rest, consequently there is an increased secretion of it. .:;^ Classes of Joints. Joints may be divided into three classes. Immovable ot Synarthrodia!, Movable or Diarthrodial, and Mixed or Amphiartlirodial. In an immovable joint there is only a thin layer of fibrous or cartilagenous material interposed between the bones. These joints are chiefly, blit not solely, found in the skull. The varieties are atltura, synchondrosis, schindylesis and gomphosis. Sutures are true and false. Variety of shape has led to the following nomenclature; sutura dentata when the Jirocesses are large and tooth -like as in the interparie- iiftl; sutura serrata where they are small and fine, like ]^e teeth of a saw, as in the interf rontal ; and sutura Umbosa, where the contiguous parts are dentated and "lilso bevelled, as in the parieto- occipital. ; In the false sutures the bones are joined by plain, libugh surfaces, of which there are two forms; sutura Iquamosa, where the adjacent borders are bevelled, the edges of one bone overlapping the other as intheparie- to-temporal, and sutura harmonia where the articulating so- s I 'J surfaces of two bones present no marked irregularity as the nasal and premaxilla. Synchondrosis resembles a sutura, but the connecting medium is cartilage instead of fibrous tissue (as be- tween the 1)asi -occipital and the basi-sphenoid.) Schindylesis is that form where a ridge or plate of one bone is received into a slit or fissure of another, as the orbito-sphenoid into the incisura sphenoidalis of the frontal bone. Gomphosis is the form where one bone is inserted into a cavity or socket in another, as the teeth in the alveoli. Diarthrosis. In diarthrodial or true joints the articular surface of each bone is covered by cartilage of encrustation. The bones are held together by ligaments, the capsular one enclosing the cavity of the joint. In some joints there is a pad of fibro-cartilage interposed between the two articular cartilages, called a meniscus, which adds to ( • freedom and elasticity of the joint. The chief varieties of true joints are arthrodia, enarthrosis and ginglymus. In arthrodia the motion is slight and gliding, as in the small bones of the knee and hock. Knarthrosis, the ball and socket joint, is capable of moving in any direction, as the shoulder and hip joints. Ginglymus, or hinge joint, although it may admit of extensive motion is limited to one plane, backwards and forwards, as in the elbow. A rotary joint (diarthrosis rotatorious) where the motion is limited to rotation, is formed by a point of one joint fitting into a ring on another (as the alto axoid joint). Amphiarthrosis. There is but one form of mixed joints. The term is used with reference, not to the motion, but to the struc- ture, which partakes of the nature of both movable and immovable, the bones being joined firmly together by a strong interposed pad of fibro cartilage which is like- wise adh'^rent to the ligaments of the joint. There is no capsular ligament. Authorities differ as to whether there are synovial membranes. The joints between the vertebral centra are the best examples. —Si- Table for Reference. Synarthrosis (Immovable) Diarthrosis (Movable) Ampharthrosis (Mixed) Sutura {Dentata Serrata Limbosa Notha Squamosa Harmonia Synchondrosis Schindylesis Gomphosis Arthrodia Enarthrosis Ginglymus Diarthrosis rotatorius Motion in Joint. The following terms express the various motions allowed in joint : Extension tends to bring two bones as nearly into a straight line as the structure of the joint wall permit. Flexion is the reverse of this. Abduction expresses the outward movement of a limb or bone from the central plane of the body. Adduction is the reverse movement of this. Rotation signifies the partial revolution of a bone or number of bones, as it were, on their own axis. Circutnduction implies the movement of the distal end of a bone or limb when it describes a curve. The term gliding describes itself. Lig'aments of the Vertebra. All moveable joints are connected by ligaments, some of which are common, others special. The former are continuous, passing over, and uniting many vertebrae, while the latter exist separately between the contiguous segments. The common ligaments are superior and inferior common, and the supra-spinous ligaments, the latter in the cervical region being called the liga- mentum nuchae. The superior common ligament ex- tends in the spinal canal from the sacrum to the axis, placed upon the superior part of the bodies of the X -52— vertebrce. The inferior common ligament situated be- low the vertebrae, stretches from the sacrum only to the sixth dorsal. Posteriorly the supra-spinous ligament is a white fibrous cord, extending from the spine of the sacrum along the upper margins of the neural spines to the first dorsal vertebra, where it changes its char- acter to yellow elastic tissue and becomes the ligamen- tum nuciite, extending forward to the tuberosity of the occiput. It consists of a funicular and a lamellar por- tion. The former is double and extends from the first, second and third dorsal spines to the tuberosity of the occiput, continuous posteriorly with the white supra-spinous ligament, in which yellow elastic tissue can be traced for some length. The right and left seg- ments meet in the median line, and from the postero- inferior aspect springs the lamellar portion, which is fiat and triangular, separating the muscles of the neck into right and left. It consists of two plates joined by cellular tissue, the bands descending from the cord and spinous processes usually of the three first dorsal verte- brse, run obliquely forward, to be inserted to the super- ior spines of the six posterior cervical vertebrae. This ligament is not a binding ligament. It is highly elastic and acts as a passive support to the head and neck, diminishing the muscular tension of the superior cer- vical region. Some of the joints of the limbs have common liga- ments, they all have special ones, with the considera- tion of which I will not burden you, but will just state that all the movable joints have capsular ligaments, most of them lateral and some interosseous. I may just mention some of the chief differences between the loints and ligaments of the ox and the horse. In the ox the sternal ribs articulate with their carti- lages by means of true diarthrosis, and are supplied with synovial membranes. The first segment of the sternum articulates with the second by means of a true joint. The pubio- femoral ligament is wanting in all the domesticated animals except the horse. Myology. The branch of anatomy which treats of the muscular system is called myology. The muscles are the active organs of motion or of locomotion, the bones and liga- ■53— ments being passive organs of the same. In order to understand their working it will be necessary to take a brief view of their anatomical and histological struc- ture . They contain a specific contractile substance called muscular tissue, together with areolar and fibrous tissue and a certain amount of fatty material. They are also furnished with nerves, blood vessels and ab- sorbents. There are tw^o varieties of muscular tissue, viz., the striped or striated or voluntary, and the unstriped or involuntary, the contraction and relaxation of the for- mer being, with little exception, controlled by the will of the animal, the latter being beyond the control of the will. The chief exception to this general distinction being found in the heart and the upper part of the oesophagus which contain involuntary striated muscular tissue. Both varieties are red in color but the hue of the striated kind is much the deeper. Voluntary muscular tissue forms the mass of the so- called muscles, which terminate at either extremity in fibrous structures called tendons, by means of which they are attached to bones, the fleshy portion is called the belly of the muscle. A muscle is composed of bundles or fasciculi of fibres. The microscope shows these fibres to consist of fine filaments termed fibrillae, which run parallel to each other. Each fibre is enclosed in a delicate tubular sheath called the sarcolemma or myolemma, composed of a transparent, tough and elastic membrane which isolates each fibre. The fibres, about 1-500 of an inch in diameter, are gathered into fasciculi, and invested with a sheath of connective tissue which is reflected between the fibres, called the perimysium internum. The entire muscle has likewise an investing sheath of connective tissue, the perimysium externum, continuous with the above. A muscular fibre, examined under the microscope will display the transverse, waving lines or striae from which the name striated is derived. Longi- tudinal markings are also often apparent but less regular than the striae. Non-Striated Muscular Tissue, or involuntary muscular tissue is pale in color, and consists of fibres bound into fasciculi by areolar tissue. -54- The fibres never terminate in tendons and are not in- vested in sarcolemma. They are cylindrical in shape, and composed of elongated cells in which a nucleus is present. The contractile power exists in the cells. This tissue is very abundant, being found in the walls of the alimentary canal and hollow viscera, in gland ducts, the coats of blood vessels, the skin and else- where. Both forms of muscular tissue are supplied with blood vessels and nerves. The nerves of the voluntary form coming from the cerebro-spinal system, and those of the involuntary from the sympathetic system. Tendons. l*he tendons in which voluntary muscles terminate at either end resemble ligaments in their composition, being formed of white fibrous tissue mixed with yellow elastic fibres, they are practically non-elastic. The ex- tremity of a muscle which has the most fixed attach- ment is called its origin, the other extremity its inser- tion. The tendon of insertion is usually the longer. The tendons are prolongations of the coverings of the fibres and fasciculi at each extremity. Fascia. Each group of muscles is invested and bound down by a strong expansion of white fibrous tissue called fascia, which is firmly attached to the bone. This term is also applied to a membranous expansion below the skin which forms a continuous covering over the whole body, composed of connective tissue more or less con- densed, this is called superficial fascia. Aponeurotic fascia is that form which covers, sup- ports and binds down groups of muscles; it unites to, and blends with the periosteum. Fascia is also found in connection with the walls of cavities, as in the pelvis. (In the limbs where muscles form lengthy masses, with long tendons, there would be considerable displacement during motion, were it not that in these parts the faF-^ia is very strong.) —55- Muscular Nomenclature. Some muscles are named from their form, others from their use, others from their situation, others from their direction, others from their attachment, &c. Time will not allow us to enter into an exhaustive study of the individual muscles, but we will consider some of the most important ones. Particular Muscles. The Pan7iiculus Carfiosus is spread over the greater part of the body, as the face, neck, thorax and abdom- inal portions, these being all continuous. It is, as a whole, aponeurotic superiorly, becoming more fleshy as it descends. It is related with the skin externally; in- ternally with the superficial layers of muscles. Its action is to corrugate the skin, and thus enable the animal to expel insects and irritating bodies. The Obliquus Abdominis Externus is situated on the infero-taleral aspect of the abdomen. It is at- tached to the outer surface of the last fourteen ribs, just below their middle, to the fascia of the latissimus dorsi, and superiorly to the lumbar fascia, to the anter- ior spine of the ilium, to the pelvis, and to the linea alba throughout its whole extent. Its action is to support and compress the abdominal viscera, and assist in defecation, urination and parturition. It is also a flexor of the vertebral column, and a muscle of expira- tion. There are also the obliquus abdominis internus, rectus abdominis and transversalis abdominis which have a similar action. Afitea and Postea Spinati muscles occupy the fossae of the scapula, and the antea is inserted inferiorly by two tendons to the internal and external trochanters of the humerus, its action being to extend the humerus on the scapula, and to bind the joint like a ligament. The />j;e and round, and lia."^, at a short distance within, an openinj<, sometimes double, which is the inferior open- injj of the lachrymal (Uict. The nostrils have the power of dilatini; and contracting considerably, their use beinj^ to .tijive passage to the air during inspiration and expiration. The Xas.il C/ianibcrs are cavities extending from the ethmoid bone \.o the nostrils, and are se])arated from each other by the septum nasi, which forms the inter- nal wall, the external is formed by the superior maxilla. Each chand)er is divided into three passages, a super- ior, middle and inferior. There are two turbinated bones in eacli cluunber, the inferior and superior. They are formed of very delicate convolutions of bones void of periosteum; their use is to augment the surface of the nasal chambers over which the olfactory nerve is distributed, while by their lightness they add very little to their weight. The nasal chambers are lined by a very i siii^Us and 2 ])airs. The former are the Cricoid. Tliyn/id and I'^pi.i^lotli.s. and the latter the Ayrtenoid antl Cnneiform. The Criioici , or rinj^-Hke cartila.^e. is sitnated at the hase of the hirynx surrounding the air ])assa<^es. The lliyroid, or shield- like cartilaj^e, is the larj^est. It consists of two lateral exjiansions which unite antero- su])eriorl_\- at a rather acute an^le forinini^ a ])rojecti()n called the hody of the Thyroid, which corresi);'n(ls to the pomum Adami innian. The Arytenoid, or ewer-sha])ed cartilaj4:cs, a pair, lie upon the cricoid, and hound snpero-])()sterioiIy the entrance of the larynx. 'I'liey are irre^nhirly ])yraniid- al, and their anterior surface forms a lip or si)out, in which rests the epij^^lottis when the larynx is closed. The Kpii^lottis is a soft leaf like cartilaj.;e, llexihle, and situated in front of the (>i)enin,s4 to the larynx, which it couipletely closes during; the passage of food to the cjesopha^us. Its anterior surface is attached *^o the tongue and hyoid hone. From its base two lateral cartilages extend backwards. These are the cuneiform cartilaj^es, a pair, and thev are situated in the folds or the mucous membrane, which stretch from the epi- )ilottis to the arytenoid cartilaj^es, to^^jether formni)^ the false vocal cords. The true vocal cords are formed by the thyroary- tenoidean lijjjaments coverel)es joined by a narrow l)an(l. The jifhind is duct- less and secretes an alhnniinous fhiid. It is lar>(e in fcetal life, but its use is unknown. The 7/iy>//iiS is another ductless )jfland, situated on the inferior aspect of the trachea, and above the ster- num. It consists of two l()l)es united by areolar tissue. In the f(ttus it is attached to the thyroid, is large at birth, gradually disappearing. Bronchi and lironchial Tithes. The terminal branches of the trachea are the right and left bronchi, which enter the lungs and sub-divide into branches, termed ])ronchial tubes, which re-divide until they become very small, and terminate in the air cells. The entire ramification, when isolated, has the appearance of a tree. The right bronchus is larger than the left. The left is longer, as it passes under the aorta before reaching the lung. The bronchi and bronchial tubes are made up of cartilaginous rings, differing only from the trachea in being made un of several pieces, which overlap and are united by cellular tissue on their inner surface. As the tubes diminish in size, the number of these pieces are diminished, and finally disappear. The air cells consist only of the lining membrane of the tubes. The Thorax, or thoracic cavity, is formed by the ribs, sternum and bodies of the dorsal vertebra;, the inter- costal muscles and diaphragm. It contains the lungs, the heart and its adjuncts, the trachea, oesophagus and a quantity of neives. The Pleura. The thorax is lined by two serous mernbranes, the right and left pleurae, which consist of parietal and visceral portions, and form two distinct sacs. Each pleura lines one-half of the thorax and half of the diaphragm, and covers the lung on that side. The portion of pleura lining the ribs is called pleura costalis, that covering the diaphragm, pleura dia- phragmatica and that covering W\^\\x\\% pleura pul- monalis. In the mesian longitudinal plane, between the lungs, it forms with the opposite pleura, the med- iastinum, which is divided into three portions. The anterior portion lies in front of the heart, the middle contains it, wh'lc the posterior lies behind it. The mediastina contain the trachea, oesophagus, heart, —77- vessels and nerves. The pleura is thick and h)().sely at' tached over the ril)s, attenuated over the dia])hra>ini and ])ericardinin, and extremely so over the lun^s. Its in- ner surf:i«'e is smooth, and secretes a vaj)ory fluid, which lu1)ricates its surface and facilitates motion. The LuHj^s, the essential orj.;ans of res])iration, are spongy or)longata. I'linary System. The organs of this svsteni secrete the urine from the blood, and excrete, or expel, it from the body. These organs are the Kiection of a kidney we find it to consist of an external or eortical , and aii internal or viadullary substance. The cortical ])ortion is a dark reddish brown and friable, consisting of min- ute blood vessels, convolutions of nriniferous tubes, lymphatics and nerves, united by areolar tissue. On examining a section with a lens red ])oints are seen, called the Malpiyjiian bodies. Kacli consists of ca])il- lary blood vessels, arranged in a tuft, surrounded bv epithelium, and enclosed in a ca])sule. the ca])sule of Bowman, which is the dilated organ of a uriniterous t\d)e. The small branch of the renal artery entering the ca))sule is the afferent vessel , whence proceed the capillaries which form the tuft. The efferent vessel leaves the tuft near the afferent (Uie. forming a plexus round the adjacent tubes, terminating in vein.s. A dark line se])arates the cotticle from th< madullary portion, which is denser in structure, fibrous in a])]iear- ance, and consists of pale conical masses, tlie pyramids of Malpii^hi . These are conijiosed of minute, diverging uriniferous tubes. In the horse they terminate in a continucms ridge, which project into the pehis, and on these ridges are the outlets. Through these outlets the urine passes into the pelvis, a cavity in the centre of the kidney formed by the dilatation of the ureter, which has lateral prolongations called the arms. The function of the kidneys is to secrete the urine, a fluid consisting of water, holding in solution a varying quantity of earthv salts, an(l a peculiar nitrogenous substance, urea, which, if not eliminated, acts as a blood poison. The Suprarenal Capsules are two small, flat, ren two individuals, a male and a female, the female furnishing a germ of ovum, and the male a fluid or sperm, which animates the germ and renders it fit for development. lioth the ovum of the female and the sperm of the male are the secretion of glands, called genital glands, and in either sex the generative system may be said to consist or these glands, with certain accessory organs. The act of coition bring the secretions in contact. Male Ueiiital Orffaiis. The spermatic, or seminal fluid of the male is elabor- ated in two glands, situated in the scrotum, called the M.. -8:- testicles, each bein^ furnished with an excretory duct, the Vas deferens, which transmits the sperm to the reservoirs, the VesicuUe Seminales, situated on the ])ladder. Here the sjjerni ac unudates, and is expelled l)y the contractile wall> of the vesicuUe durinj^ the act of copulation, throuj^h the ejaculatory (Uicts into the urethra, which is common to the urinary and genital organs. The urethra is provided with accessories, the prostrate and Cowper's glands. ;nid is supported by an erectile tissue which forms an elongated organ, the ])enis. The Scrotum is a sac. or bag, which contains the testicles, situated between the thighs, and made up ex- ternally of a layer of skin. It is nnirked in the middle by a longitudinal raphe, indicating its division into right and left cavities. Below the skin is a thin layer of muscular and elastic tissue, forming a tuinc called the darlos, which sends in a fold between the testes called the septum scroti. The luij^uifiat Cauals are slit like a]iertures in the posterior part of the floor of the abdomen, through which passes the spermatic cord in the male, and the mammary vessels in the female. The external orifice is called the c.vtcruat iuouiual /iu,^\ and the internal ori- fice the iuternal iuguiual rin^, and the space Ijetween the iugiiiualcauaf . The Spermatic cord suspends the testicle in the scro- tum (one to each testicle). It is made up of the Vas deferens, blood vessels, nerves and serous membrane, muscular tissue and fascia. It extends from the ingui- nal canal to the testicles, certain coverings being com- mon to it and the latter. The Testictes are two oval glands, situated in the scrotum, :tached superiorly to the spermatic cord. In foetal ife they are at first situated behind the kid- ney, and above the ])eritoneuni. At a certain period they descend through the inguinal canals into the scro- tum. In their descent each is guided ])y a soft cord, the ^ritfyeruacutuin testes. In their descent they carry with them coverings derived from the abdominal ])arieties, also coverings composed of peritoneum. The first tunic proper to the testicle is the tunica alhui^inea. which is reflected into its substance, forming a septum called the mediastinum testes, from which processes T 1!^ -82— are sent out dividing the testicle into lobes. Inside of this tunic we have the tunica vasculosa enclosing the testicle and giving off vascular processes to it. The testicle is divided into from 200 to 300 distinct lobes, which consist of numerous tubes with csecal ends, call- ed tubuli seinifii/eri in which the semen, or sperm, is secreted. The Epididymis is an elongated body extending along the upper border of the testicle. It consists of a body, a head, and a tail. The body is free and curved to the shape of the testicle. The head, situated anter- iorly, is adherent to the testicle. It is the largest part and gradually becomes slimmer towards the body. The epididymis is composed of small convoluted tubes, which join and become larger until they form one single tube, the vas deferens. • The Vas Deferens is a tube with solid walls, which, after leaving the epididymis, ascends the back part of the spermatic cord to the inguinal canal, where it leaves the cord, enters the pelvis, and passes to the neck of the bladder, where it is joined by the duct of the vesicula seminales, the two forming the ejaculatory duct. The Vesinilcr Seminales are two pear-shaped, glan- dular pouches, situated on each side of the postero- superior aspect of the bladder, and between it and the rectum. They are receptacles for the semen, and secrete a special fluid which mixes with the semen. The ejaculatory ducts are right and left, formed by the junction of the vas deferentia and the vesiculse seminales. They terminate in the urethra by two orifices. The Uterus Masculinus represents in the male, the uterus in the female. It is a canal about four inches long, which ascends in the folds of the peritoneum be- tween the vas deferentia. Its lower end is situated be- tween the ejaculatory ducts. The Prostrate gland is situated around the neck of the bladder and commencement of the urethra. It varies in size, and consists of three lobes, a middle and two lateral. The middle one lies on the neck of the bladder, and in old age sometimes becomes enlarged, and presses on the urethra, causing retention of urine. The secretion is excreted by ducts into the urethra. —83— Cozvpers ^i^huids are a pair of small bodies, situated on either side of the membranous portion of the urethra, above the ischial arch. They reseml)le the prostrate gland in structure, and terminate in the urethra by a row of minute openings on either side. iLh^'Urethra is a tube which extends from the neck of the bladder to the glans penis in the male, and to the vulva in the female. In the latter it is merely an excretory passage for the urine, but in the male it also transmits the seminal fluid. The pefits is the male organ of copulation. It con- tains the greater portion of the urethra. It may be said to consist of an attached and a free portion, the first originating at the ischial arch, and terminating before the brim of the pubis, where the free portion commences. The penis is formed of what is called erectile tissue, which, under certain circumstances, becomes enomiouslv distended with blood. The erec- tile structures are two in number, the corpus caver- nosum and the corpus spoufriosum. The corpus cavernosum is much the larger, and forms the superior and lateral portions of the penis. This portion is in- vested by a strong, elastic, fibrous tissue, wliich sends out processes dividing the structure into numerous compartments which receive the blood during erection of the organ. The corpus spongiosum encloses the urethra, and is situated in a groove in the inferior por- tion of the corpus cavernosum. At the anterior ex- tremity it expands to form the ^^lans. At the apex of the glans is a deep fossa, in the centre of which lies the tneatus urifiarius. The Sheath is a loose fold of integument, which in- vests the free portion of the penis. It forms a sac ex- tending from the scrotum forward. Anteriorly a loose fold of the sheath projects, covering the anterior ex- tremity of the penis when quiescent; this is the prepuce or foreskin, and from it the skin contines in a modified form over the glans, while it covers and becomes continuous with the mucous membrane of the urethra. The corrugations of the prepuce admit of the erection and protrusion of the penis. Opening on its inner surface are the glandulce odoriferce^ which secrete a peculiar odorous matter. ■*,-. 1 ^ -84— The Seinina/ Jhtid. The secretion of the male genital orj^ans is a viscid, whitish al])uininous fluid the sperm or seminal fluid, which contains tlie sprrnia- tozoii, microsco])ic o])jects consisting each of an ovid head and a loii^ wavy tail. They possess a certain vibratory motion, and have the power of penetratinj^ and fertilising^ the female ovum. The female i^cuital origans are the oi'aries which furnish the oi'iun or jjjerni of the future animal. The ovum is conveyed alou}^ the Fallopia^i tube to the uterus, a cavity in which it becomes im])regnated by the sperm of the male, and developed. The vaj^ina is a tube or cavity analogous to the urethra in the male, common to the urinary and genital systems, the uterus opening into it anteriorly and the meatus urinarius being situated at its posterior boundary. The Ovaries, being the analogues of the testicles, are the ultimate organs of generation in the female. They are similar in shape, l)ut smaller than the testicles, and are situated in the sublumbar region of the abdomen, a little ])ehinil the kidneys, their tunic resembling that of the testicles, is a dense tuniea alhuiiiuea. With- in are numerous small b.odies, called the Graafian ves- icles, which contain a fluid in which the true ovum resides. This fluid is secreted 1)y the cells of this vesicle. It increases in quantity as the vesicle de- velo])es. During the period of heat or vest rum the walls burst, and the fluid with the ovum escapes into the l'alloi)ian tube and is carried to the uterus. The ovum is, in the higher animals, microscopic, being about 1-150 of an inch in diameter. The Fallopian Tubes are two canals which convey the ovum from the ovaries to the uterus. They run in a serpentine route from v ach uterine horn to the ovary. Each commences in a ve- v minute opening, the ostium uterinum, and lenninatts in a small orifice, the ostium abdominale, wliub communicates with the abdomen. The free extremity of tlu- tube terminates in a series of fringes which are arranged in a circle around the ostium abdominale. One of these fringes is attached to the ovary and along it is a fissure, continuous with the external opening of the tube. The fringes embrace the ovary during sexual excitement, receiving the ovum on rupture of the vesicle and conveying it to the fallo- pian tube. —85— The Uterus, or womb, is a iinisculo inembrnnous sac situated in the subhuiibar region ami )>elvic cavity. It consists r f a body and two Iiorfis. The body is cylin- drical and somewhat flat. Its superior surface contacts the rectum, which passes between the horns. The an- terior extremity is continuous with the horns, and the posterior with the vagina, constituting^ the iicck , which is thick and round, and projects into the vagina in the virgin animal; in its centre is a canal, \.\\^t as uteri, leading into the body. The horns spring from the anterior extremity of the body, diverge upwards and forwards, communicating with the I'allopian tube. The uterus consists of three coats, an external serous, middle muscular and an internal mucous. The serous coat is a reflection of the peritoneum, it forms the broad liga- ment which suspends the uterus. The ]'a^i^i?ia is a canal leading from the uterus to the vulva. It is wide and surrounds the neck of the uterus, but is constricted at the vulva. It is the chief female organ of coition. The J'uti'ais the external orifice of the urino-genitial system, is situated below the anus. a])pears as a long ovid slit, presenting two lips and two commissures. The lips have an external covering of soft skin, and an inner one of mucous memlirane. Between these is a (juar.tity of fat and areolar tissue, and some erectile tissue. This structure is charged with blood during copulation, rendering co-aptation very complete. In a depression on the floor lies the el if or is, which is com- posed of erectile tissue and becomes erect during copu- lation. The external orifice of the urethra, the meatus urinaries, open on the inferior surface of the vulva, ai)out four inches from the external opening. It is larger than the male ()])ening, and is surrounded by a fohl of mucous membrane, which acts as a valve. The Hytneu is a thin semi lunar fold of mucous membrane, which imperfectly separates the vulva from the vagina, lying immediately before the meatus. It is ruptured during the first act of copulation. From v.he above descriptions it will be apparent that in the male animals the female organs are indicated, as are the male organs in the female. Thus in the male the uterus masculinis represents an undeveloped ute- rus, and in the female the clitoris, a rudimentary penis. r T^ —86- This points to the fact that in early foetal life there is jio distinction of sex. each animal having rudimentary male and female generative organs. Should both sys- tems of organs in the same animal become more or less developed, but neither of them perfectly so, the animal is said to be heytnaphrodite . The Mammary Glands in the young female, as in the male, are rudimentary, becoming developed in the former at puberty, or when the animal is fit for repro- duction. In the mare these glands are two in number. In full activity they present 2 hemispherical masses, separated by a shallow fissure, each half presenting in its centre a nipple, or teat^ pierced at its free extremity by numerous orifices for the passage of milk. The ■interior of the gland is made up of yellow glandular tissue, consisting i>f numerous lobes united by a cellu- lar tissue ; each of these is again made up of small lobules composed of minute ducts and numerous small cells, in which the milk i'i secreted, and conveyed to the ducts, which unite to form a common excretory duct for each lobe. These ducts converge to the centre of the gland where they terminate in dilated cavities, the lactiferous sinuses which conmmnicate with each other. From these proceed a number of canals which run to the free extremity of the teat by constricted orifices. The mucous membrane of the teat is sur- rounded by muscular fibre, which acts involuntarily as a sphincter, and retains the milk. The base of the teat is surrounded by certain glands secreting a lubricating fluid which protects the teat during the sucking of the young, and prevents the plugging of the orifices by coagulation of the milk. Comparative Anatomy. We will now briefly consider the four systems we have been studying, and note the principal differences between the anatomy of the horse and ruminants. The lips of the ox are thick and only indirectly pre- hensible. The centre of the upper lip is devoid of hair and constitutes the muzzle, and in health is al- ways moist. The lips of smaller animals are thin, very mobile, and are agents of prehension. The cheeks of ruminants present on their inner surface conical papillae which point backwards. The soft palate is not is —87 vSO complete and pendulous as in the horse, thus per- niittinj^ the animal to hreathe through the month and allowing the upward passage of food. The tongue of the ox is prehensible, and is rougher, shorter and thicker than in the horse, and pointed at the tip. The ox and sheep have no incisor teeth in the upper jaw, but instead have a thick cartilagenous pad witli which the lower incisors come in contact in cropping grass, etc. The incisors are eight in number in the lower jaw, and have a certain degree of mobility which pre- vents injury to the pad. The oesophagus is well de- veloped, and its muscular walls are red throughout, and joins the stomach by expanding. The muscular fi])res induce both a downwards, or a peristaltic and an upwards, or anti -peristaltic, motion. The Stomach of ruminants is a very complex organ, consisting of four compartments, which vary in size and form, and in the disposition of their mucous coat. The first is the rumen, or paunch, the second the r^Z/V- Ulum, or honey comb, the third the omasum or many plies, and the fourth the '^omasum or true digestive stomach. The first three are principally concerned in preparing the food for the fourth, and have little to do with the essential process ot digestion. The rumen is very large, occupying about three-quarters of the abdomen. It is situated on the left side. The surface is smooth and divided into two lateral regions by a groove. The anterior extremity receives the insertion of the oesophagus, and is continuous with the second compartment, and is bounded anteriorly by the second and third, and the diaphragm. The pos erior occupies the entrance of the pelvic caviiy, where it contacts the urino-genital organs. In the female the uterus is prolonged over its surface. The superior surface is related with the intestines, while the inferior rests upon the floor of the abdomen. The left side, to which the spleen is attached, is in contact with the abdominal walls in the lumbar region. The interior is incom- pletely divided into four sacs by fleshy pillars. The mucous coat is cuticular, papillated, and covered by thick epithelium. The reticulum is the smallest of the four, and is situated between the diaphragm and the rumen. The internal surface is divided into polyhedral cells by folds of mucous membrane. It communicates — 8S— with the ruiiRMi, tht* cus()])haj4iis and the oniasuin. The coiniiiunication with the hitter two is by the oesopha- geal canal, a continnation of the ciesopha^^ns, which commences at the cardiac orifice, passes alonj^ the roof of the reticnluni and enters the omasum by a circular opening. Its sides consist of two nu>vable lips, which are continuous with the muscular walls of the oesopha- gus, and are attached by one border to the superior wall of the reticulum, the other being free. There are transverse and longitudinal fibres in the muscular coat of this canal. The longitudinal fibres by contracting draw the lips together, forming a channel leading from the oeso]diagus to the onmsum, thus effectively closing the opening into the rumen and reticulum. The Omasum is also situated between the diaphragm and the rumen, and when full is ovid. The left ex- tremity is constricted, forming the neck, by which it comnumicates with the reticulum. The interior is filled with leaves, or folds of mvicous membrane, which follow the long axis of the organ. Between each pair of large we have small leaves, which extend a limited distance oidv. Ihey consist of an inner framework of muscular fibres, clothed with mucous membrane, studded with ])a])ilUe, some of which are small, others large and bent, the latter retaining crude portions of .food for further trituration and maceration, while fluids and finer ])ortions pass directly to the abomasum. The Abomasuvi, or true digestive stomach, is con- tinuous with tlie omasum and duodenum, from the latter it is separated by the pyloric ring. The interior re- sembles the villous portion of the stomach of the horse, having glands and follicles which secrete gastric juice. The process of rumination is believed to be effected as follows: The food being swallowed falls into the rumen, where it is tossed about by the muscular action and saturated with fluid, a portion is thrown through the valvular opening into the reticulum, and gains a further supply of fluid, and the finer particles are separated from the coarser, the former proceed to the omasum, the latter, by the muscular contraction of the reticulum, the relaxation of the oesophageal pillars and the anti-peristaltic action of the oesophageal walls, is returned to the mouth to be remarticated, and once more swallowed. .lUy coarse portion again falls into —89— 7 ':»f, the rumen to be reacted on, the remainder passes down the oesophageal canal to the omasum, whence licjuids flow into the abomasum, whik" solids are drawn between the leaves of the omasum to be further ])re])ared. The small iulcstinr differs little from thatof the horse, except that it is smaller in calibre but on an average twice the length. There is no distinct separation be- tween the great and floating ccdon as in the horse. The total lengtli of the large intestine in the ox from the Ccfcum to the rectum is 36 feet, but its capacity is much less than that of the horse. The Liver of the ox is very thick, and is ])rovided with a pear-shaped gall bladder lying upon its posterior surface. The duct of the gall bladder enters the duo- denum singly, not connecting with that of the pan- creas, as in the horse. Respiratory System. There are not many important differences. We may note the presence of a third bronchus which passes to the right lung to sup])ly a lobe which is wanted in the horse. The left lung is divided into 2 lobes, the right into 4. The interloi)ular cellular tissue is exceedingly thick, the separation between the lobules being . ^> ^ ^ ^ IMAGE EVALUATION TEST TARGET (MT-3) 7 ^ A .// .V MP, V % Vx s W- fA 1.0 I.I m 1^ y. MM dO M 2.2 2.0 .8 1.25 1.4 1.6 -< 6" — ► V} <^ /i 'a ^>, ■^^# - W^: •■/ .V' /.^ y /^ Photographic Sciences Corporation 33 WEST MAIN STREET WEBSTER, N.Y. 14580 (716) 872-4503 <{^ L ii —90— Female Organs. In the female the ovaries are comparatively small. The uterus presents generally the typical arrangement, but the mucous membrane presents a number of round- ed vascular processes which exhibit eminences and de- pressions, these are termed maternal cotyledons and their function is a foetal one. The mammary glands in the cow constitute an organ called the udder, which is composed of two symmetrical halves placed one against the other. Each half is again divided into 2 distinct glands, each with its own teat, so that the udder con- sists of 4 mammte and 4 teats; behind these there may be two rudimentary teats. There is but one excretory channel in each teat. In the small ruminants there are 2 mammae and 2 teats constructed like those of the cow. Aiig-ioloffy. Under this head we describe the organs of circula- tion, by the action of which certain fluids are propelled through the body. We will divide it into two sections, the Blood- Vascular and Lymphatic system. Tlie Blood- Vascular System. This involves the Blood, Heart, Arteries, Veins and Capillaries. The Blood is a fluid which nourishes all living struc- tures, being the medium by which nutritive material is conveyed to, and effete material conveyed from the solid tissues. Its color varies in different parts of the same animal, that in the arteries being bright red or scarlet, while that in the veins is of a dark purplish hue. Microscopically examined it is found to consist of minute corpuscles, and a clear, yellow fluid, "the liquor sanguinis ^^^ in which the corpuscles float. The corpuscles are of two kinds, the red and the white, the former are nuicli more numerous and vary in shape. In mammals they are more or less discoid and bi concave, their avenige diameter being one-four-thousandth part of an inch, and thickness one-quarter of this. The white corpuscles are larger, round and nucleated. The liquor saus:uinis is pale and clear and consists of water, fibrin, albumin, fatty compounds, oderiferous and —91— saline matters. The serum consists of liqnor sanguinis deprived of fibrin. It contains 90 per cent, of water and coagulates when heated, owing to albumin. lMl)rin is a wliite, stringy, elastic substance which is in solu- tion in circulating l)lood and cannot be distinguished from other constituents of liquor sanguinis. The Heart is a hollow, involuntary, muscular organ, situated between the layers of the middle mediastinum, and in the pericardial sac. Its form is that of a blunt cone slightly flattened from side to side, and it presents a base and an apex. The base is turned upwards and towards the dorsal vertebra?, from which the heart is suspended by the blood vessels. The apex points down- wards, backwards, and to the left side, lying at about the level of the last bone of the sternum. The organ extends from about the third to the sixth rib inclusive. The average weight of a horse's heart is about six and a half pounds, its length about eight inches, its antero posterior diameter rather less, its lateral diameter less still The heart is divided by a longitudinal septum into a right and left side. Kacli of these is again sub- divided by a transverse septum into two compartments which communicate. Thus there are four cardiac cavities, the superior ones, whose free extremities somewhat resemble a dog's ears, are called the a it rie/es, the inferior ones, the i'e7itrieles. These divisions are marked externally by deep grooves, in which the car- diac blood vessels run and which are usually filled with fat. Tw^o of these grooves extend from the base of the ventricles to the apex, and are called the anterior and posterior longitudinal furrows. Around the base of the ventricles is a deep transvense auriculo-ventricular furrow which marks the division of the heart into an upper or auricular and a lower or ventricidar portion. The right side of the heart is sometimes called the ve7ious and the left the arterial side. We will first consider the cavities of the right and then those of the left. The Ri^i^ht Auricle is the larger and forms the right and anterior portion of the base. It presents 2 cavities, the sinus venosus and auricular appendix. The former, the principal cavity, has thin walls and is connected inferiorly with the right ventricle, internally with the left auricle, and prolonged anteriorly to form the If /J —92— appendix, a small conical pouch with thick wall and serrated edges. On laying open the auricle we notice the smooth, transparent Endocardium, or lining mem- ])rane, the anterior and posterior Vena-cavae, Coronary sinus, Foramina Thebesii and the right Auricular Ven- tricular opening. The anterior Vena-cava opens into the supero-posterior part of the sinus venosus. The posterior Vena-cava opens into the infero-posterior part of the external wall of the sinus. The Coronary sinus is below the opening of the posterior Vena-cava ;through it the blood is returned from the substance of the heart, the coronary valve covers the opening. The Foramina Thebesii are minute openings on the inner surface of the auricle, being the openings of small veins which return the blood directly from the walls of the heart. The right Auriculo-ventricular opening is large and oval, occupying the floor of the auricle and communi- cating with the right ventricle. On the Auricular sep- tum is a depression, the fossa ovalis^ the remains of the forajnen ovale. There are columns of muscular fibres chiefly in the appendix called inusculi pectinati^ from their resemblance to the teeth of a comb. The Right Ventricle occupies the antero-inferior part of the right side of the heart. Its walls are thicker than those of the auricle but thinner than those of the left ventricle. On laying the cavity open two openings are seen. The auriculo-ventricular communicating with the auricle, is surrounded by the auriculo-ventri- cular ring, and guarded by the tricuspid valve, which is formed by a doubling of the lining membrane, strength- ened by fibrous tissue. It consists of 3 triangular seg- ments, which, connected at their bases, surround the opening. The edges are thick, and to their ventricular surfaces are attached a number of tendinous cords, the chorda; tendinece, which spring from the tnuscnli-pap- illaries and the inner surface of the ventricle. The valve prevents regurgitation of blood into the auricle when the ventricle contracts. The second opening is the origin of the pulinonary artery. It is above and to the left of the auriculo-ventricular opening, and is guardcil by three semi-lunar or segfnoid valves, which consist of folds of lining membrane, and are attached by their convex margins to the tendinous ring which sur- rounds the opening. Their free edges are nearly -93- straiglit and thinner than their attached ones. When blood passes from the ventricle to the pultnonarv arterv the valves are placed against the sides of the' vessef; when the current is checked a portion of it falls back towards the ventricle, and the valves are thrown in- wards and completely close the tube. Behind the valves, at the commencement of the artery, are three dilations or pouches, bounded 1)elov/ by the valves themselves, and called the si?iiises of I'alsalva. From the inner surface of the ventricular walls project the fleshy columns, or Caniecr Columno', which form a net- work from which the chordae tendime spring. The Left Auricle is smaller th;ni the right, 1)ut its walls are thicker. It is situated at the left postero- superior part of the heart and consists of a sinus and an appendix. On laying open the cavity we find the openings of the pulmonary veins, usually two pairs, one pair on the right and the other on the left of the sinus; they are not guarded by valves. On the floor is the auric ulo-ventrictilar opening, communicating with the left ventricle. The Left I'entricle is larger, rounder, and more prominent than the right, projecting lower and forming the apex. Its external wall is thicker than that of the right. On laying open the cavity two openings are seen, the left auriculo-ventricular opennig and the aortic. The former is guarded by the bicuspid or mitral valves. The valves have the same general characiers as the tricuspid. The aortic opening is deeply seated in the supero- anterior part of the ven- tricle, a little to the right of the auriculo-ventricular opening, from which it is separated by one of the seg- ments of the mitral valve. It is guarded by three semi- lunar valves similar to those of the right side, but stronger. The rest of the inner surface has the same general characters as the right side. The Structure of the Heart consists of a fibrous frame work, muscular and connective tissue, vessels and nerves, the whole being covered by one, and the cavities lined by another serous membrane. The mass of the heart is composed of nmscular fibres connected by areolar tissue. The fibres are involun- tary, and of a deep red color, differing from other in- voluntary muscles (the oesophagus excepted) , in being -94- transver.sely and longitudinally striated. They are smaller than voluntary fibres and are anastoniatic. The muscular fibres are attached to a frame work which consists of fibro cartilaginous rings surrounding the auriculo-ventricular and arterial openings. Be- tween the aortic ring and the auriculo-yentricular open- ings is a fibio cartilaginous mass which in the ox is re- placed by a bone, the os cordis. The Endocardiiiin is the name given to the serous membrane which lines the cavities of the heart. It is continuous with the lining membrane of the blood yessels. The Pericardium is a fibro serous sac which encloses and is reflected over the heart and origins of the large blood yessels. It is composed of two layers, an exter- 4ial fibrous and an internal serous. The serous secretes a pale, lubricating fluid, the liquor pericardii. Course- of the Circulation. The yenous blood is car- ried into the right auricle by the anterior and posterior yena-cavse, passes through the right auriculo-yentric- ular opening into the right yentricle, thence through the pulmonary artery to the lungs. It returns through the pulmonary veins to the left auricle, passes through the left auriculo-yentricular opening to the left ven- tricle, which propels it through the aorta and its branches into the system generally, the yeins returning it again to the heart. The circulation therefore is double. The pulmonary, or lesser, being performed by the right side; and the Somatic, or greater, by the left side of the heart. The Arteries are tubes conveying the blood from the heart, a series belonging to each circulation. Both arteries leave the heart by a single trunk which sub- divides and terminates in capillaries whence the yeins originate. The large arteries are usually deep seated, occupying the nyities of the trunk and inner surfaces of the limbs, where they are less exposed to injury. When they pass oyer an articulation they are usually found on the flexor side. Arteries freely communicate with each other, forming what are called anastomoses. Arteries are dense and elastic, possessing great power of resistance. Their walls consist of three tunics, an external, middle and internal. The internal, or serous, is thinnest; the middle tunic is contractile, elastic, —95- dense, and of a yellow color, consisting of non striated muscular tissue and elastic fibre; the external coat is made up of areolar tissue and elastic fibres. The arterial sheaths consists of cellular tissue intimately connected with the surrounding textures. An artery is usually accompanied by a vein and nerve, all of which may lie in the same sheath, the vein being more superficial. The coats of arteries are supplied with nutrient blood vessels, the vasa vasorum, which come from neighboring vessels. The external coat is very tough, while the middle and internal ones are elastic and brittle; on ligaturing an arter^^ the middle and internal coats give way, while the external remains intact. The Capillaries; are interposed between the termin- ation of arteries and the commencement of veins, form- ing plexuses which vary much in arrangement. Their average diameter is about one three -thousandth of an inch, varying in different textures, smallest in the brain and mucous membrane of the intestines, largest in the skin, in glands, and the inter or of bones. All arteries do not terminate in capillaries, an exception being in the erectile tissue, where they end in cells or cavities placed at the origin of the veins. The Puhnoiiary Artery springs from the right ven- tricle, curves upwards and 1)ackwards, and divides into right and left branches, which penetrate the substance of their respective lungs, along with the bronchii, rami- fying in the lung along with the bronchial tubes and terminating in capillaries, which form a dense network on the walls of the air cells, the branches belonging to different lobules do not anastomose; from these capil- laries spring the radicles of the pulmonary veins. The pulmonary is the onl}' arterj^ in the adult that conveys venous blood. The Common Aorta is the main trunk of the arterial syvStem. It arises from the left ventricle, passes up- wards and forwards for about two inches, then divides into anterior and posterior aortse. The former supply- ing the fore extremity, neck and head, and the latter the rest of the body and limbs. Coronary Arteries. — In addition to its terminal branches, the aorta gives off right and left coronary or cardiac arteries, which nourish the tissues of the heart. ^96— The /\^sterior Aorta is larger and lonjj^er than the anterior. It commences about the level of the 4th dorsal vertebra, passes upwards and backwards, form- ing the aortic arch, reaches the left side of the spine at the 6th or 7th dorsal vertebra. It passes straight backwards through the haitus aorticus to the abdomen, and terminates at the posterior part of the sublumbar region by dividing into external and internal iliacs. It is divided into thoracic and abdominal portions. It furnishes parietal and visceral branches. Parietal Branches. Aortic Intercostals Lumbar Phrenic Middle vSacral The Intercostals are doublets, 17 in number, the last 13 of which arise directly from the posterior aorta (the first arises from the superior cervical and the nex three from the dorsal artery.) The intercostals, after leaving the trunk skirt the dors»l vertebra, and divide into inferior or intercostals and superior or dorso- spinals. The former branch is the larger, and travels along the grooved posterior border of the rib down the side of the thorax, and supplies the pleura, intercostal and thoracic muscles. The dorso-spinal branch is dis- tributed to the dorsal muscles and integument, and supplies the cord and its coverings. The Lumbar arteries, 5 or 6 pairs, originate like the ''ntercostal and divide into superior, or lumbo- spinal, which supply the muscles of the loins, and send branches to the cord, and inferior which supplies the abdominal muscles. The Phrenic supplies the dia- phragm. The middle sacral is a mesian continuation of the posterior aorta, often absent in the horse. Visceral Branches. Broncho - CEsophageal — Thoracic . Coeliac Axis^ Great Mesenteric^ Small Mesenteric^ Renal. Spermatic Small Testicular. Abdominal. -97- Tlie Bronchial sup])ly the Iuiiks, the ivsopliaoca/ the oesophagus. The Cccliac axis arises from the lower surface of the aorta as it enters the al)donien ; is a])out an inch lonj/, and divides into Gastric, vSplenic and Hepatic. The gastric is distributed to the stomach; the si)lenic to the spleen, and the hepatic to the liver, pancreas, and pyloric end of the stomach. The Great Mesenteric arises a little behind the c(x?liac axis and splits into right, left and anterior divisions. It is distributed to the niesentry, from it twigs proceed to the small intestine and to a portion of the large. The Small Mesenteric artery arises three or four inche;s behind the great mesenteric. It supplies the floating colon and rectum. The Renal arteries are right and left, leave the aorta at right angles, and pass straight to the hilus of the kidney; an anterior branch supplies the suprarenal capsule. The Spermatic arteries, right and left, become, in the female, the utero-ovarian . Their diameter con- sidered, they are the longest arteries in the body, and they give off no lateral branches; pass through the inguinal canal down the anterior border of the sper- matic cord. The Utero-Ovarian arteries supply, in the female, the uterus and ovaries. The Small Testicular, or artery of the cord, is small, passes through <^he inguinal canal, and supplies the tissues of the cord, first giving branches to the ureter, vas deferens and peritoneum. The Posterior Aorta, at the level of the last lumbar vertebra, gives off the external Iliac arteries, and a little posterior to this the rest of the trunk bifurcates, forming the internal Iliac arteries, which are short, thick trunks. They supply the pelvic viscera, and par- tially the muscles of the hindquarters. The External Iliac arteries arise below the last lumbar vertebra, curving obliquely outwards and downwards. At the level of the ileo-pectineal line it becomes the femoral. The external Iliac gives off the circumflex ilii. The Femoral is the artery of the thigh. It runs to the inferior part of the off femor, -98— becoming the Popliteal. In its course it j^ives off various b-atiches which supply the muscles of the thij^h. The l'o])liteal passes under the po])liteal muscle, and at the upper part of the tibia bifurcates into anterior and posterior Tibial. The posterior tibial passes down the posterior part of the til)ia to the hock, to which it ^ives branches, and then divides into internal and external Plantar ^ each of which cliuj^s to its own side of the deep flexor tendons, pass- inj< down to the fetlock. The anterior tibial passes down to the hock, where it becomes the 3fetatarsal, and passes down to the fetlock and joins the ])lantar arteries, from which proceed the arteries of the foot. The Anterior Aorta is rather more than an inch in length and passes obliquely upwards and forwards ; it divides into rij^ht and left arteria innominata, or bra- chial arteries. The Braehial arteries separate at an acute angle'J and pursue a diverging course towards the anterior aper- ture of the thorax, whence they proceed to the limbs, winding round the first ribs, the right one, being the largest, gives off the common carotid. The following arteries are given off alike by both brachial arteries: — the Dorsal, Superior Cervical, Vertebral, Internal Thoracic, External Thoracic, Inferior Cervical, Pres- capular and Subscapular, each of which supplies the region its name indicates. When the brachial reaches the humerus it assumes the name of the humeral artery and descends along the inner side of the hum- erus to the elbow joint, just below which it becomes the posterior radial artery, having in the meantime given off the anterior radial and a number of small branches. It passes down the inner side of the forearm and divides at the distal end of the radius into large and small metarcarpals. It can be felt just behind the insertion of the flexor brachi. The large fuetacarpal is the true continuation of the posterior radial, and it descends along with the flexor tendons to just above ihe fetlock, where it divides into the external and internal digital arteries. The Common Carotid artery is given off by the right brachial. On reaching the anterior opening of the thorax it divides into right and left carotids which pass up the neck, one on each side of the trachea, to a level CO fot Ca an( -99- with the larynx, Kiviii}^ off several brandies in their course. At the larynx each terminates in a trifurcation forniin)> the follo\vinj< arteries; The Occipital, Internal Carotid and ICxternal Carotid. The ^rr//>/A// ascends and passes throuj^h the anterior foramen of the atlas, supplying the muscles of the ])oll. and sendin^j a branch into the spinal canal, joins with its fellow of the oj)])!)- site side, forming the bassilar, which passes alon^ the base of the brain. The intenial carotid ])asses throu»^di the foramen lacerum basis cranii and is distributed to the brain. The extenial carotid is the continuation of the carotid itself and it supi)lies the muscles of the mouth, face, ears and eyes. Veins are vessels which return the blood to the heart, and they consist of two sets, the pulmonary, which convey arterial blood from the hnij^s to the left, and the systemic, which convey venous blood from the somatic capillaries to the rij /v.? and cells are found. The fibres convey impressions to the centres, and transmit stimula from the centres to tlie various organs. Those which convey impressions are termed sensory nerves, and those which transmit stimuli to the muscles are called motor nerves, those to the coats of blood vessels vasa motor. The cells are found chiefly in the nerve centres and they germinate nervous force. This reflec- tion of nervous impulse from one nerve to another is known as reflex action. The centre of the cerebro- spinal svsteni is the cerebro- spinal axis, consisting of the brain and spinal cord, which, with their coverings or meninges are continuous with one another. Meningres of the Spinal Cord. The cerebro spinal axis is invested by three distinct membranes, viz.: the dura mater externally, the arachnoid in the middle, and the pia inater internally. The dura mater is a strong inelastic membrane. It extends from the foramen magnum, to which it is at- tached, and is continuous with the dura mater of the brain, to the posterior extremit}- of the neural canal, where, as a slender cord, it blends with the periostum of the first bone of the coccyx. It is loosely attached to the inner surface of the canal b}^ a layer of areolar tissue and bloodvessels. The Arachnoid, so-called from its resemblance to a spider's web, is a delicate serous membrane, and like other serous membranes, is a closed sac. It loosely envelopes the pia mater, leaving between them an in- terval, the sub- arachnoid e an space, which contains the limped cerebro spinal fluid. The Pia mater, the inner envelope of the cord, is a thin vascular membrane, composed of areolar tis.sue containing blood vessels. It closely invests the whole —104— surface of the cord, sends processes into its longitud- inal fissures, and forms a sheath for the spinal nerves. The spinal cord is a large, white, irregularly cylin- drical cord, which extends from the foramen magnum to the sacral portion of the neural canal, where it terminates in a slender filament. It is loosely sus- pended in the. canal to allow motion. It varies in size; is dilated at its origin, where it joins the medulla oblongata, and also between the 5th cervical and 2nd dorsal vertebrae, where the large nerves which form the brachial plexus are given off, and again at, and posterior to the 3rd lumbar, where the lumbar and sacral nerves which constitute the lumbo -sacral plexus arise. The cord is divided into two lateral col- umns by longitudinal fissures, superior and inferior. Each side is again divided conventionally into three parts by lateral fissures, a superior corresponding with the sensor}^ and an inferior with the motor roots of the spinal nerves. A transverse section of the cord shows the white matter externally in the form of two semi- cylinders, and the grey matter in the centre of each. The grey substance presents the appearance of two crescentric shaped masses united in the middle b}' the grey commissure. Each crescent presents two cornua or horns. . In the middle of the grey commissure the central spinal canal runs the whole length of the cord, being continuous anteriorly with the 4th ventricle of the brain. The proportionate size of the brain and spinal cord varies in different animals, according to the position which they occupy in the scale of intelligence. The higher that postition the larger and heavier proportion- ately is the brain, and the smaller and lighter the cord relatively. Thus in man the brain averages 50 oz and the spinal cord 1 V2 oz, a proportion of 1 to 33. In the horse the brain averages about 23 oz and the cord lOJ^ oz, a proportion of 1 to 2-19. The E7icephalon, or brain, is that part of the cerebro spinal axis situated within the cnnium. In form it is a slightly flattened and elongated ovoid body, which may be considered as consisting of 4 parts, viz., the medulla oblongata, the pons Varolii, the cerebellum and the cerebrum. It has coverings like the cord. ^- —105- The Medulla oblott^ata is the proloiij^atioii of the spinal cord, extending to the pons Varolii, from which it is separated by a narrow fissure. It is pyramidal in shape, the narrowest part being continuous with the cord. The Pofis Varolii is a transverse projection on the base of the brain between the medulla oblongata and the crura of the cerebrum. The Cerebellum, or lesser brain, is lodged in the pos- terior part of the cranial cavity, immediately above the medulla oblongata. The Cerebrum, or great brain, occupies the anterior portion of the cranium. It consists of lateral halves separated by the longitudinal fissure. Deep sulci map out the surface of the hemispheres into numerous con- volutions, the number of which and the depth of the sulci indicate the range of intelligence possessed by the animal, as the grey matter, which is believed to be the seat of the intellectual faculties, is found on the surface of the convolutions, and on the sides and bottom of the I sulci, so that the deeper and more numerous these are the greater is the amount of grey matter in the brain. Functions of Different Divisions of the Brain. The Medulla oblongata is the conductor of impres- sions. The majority of centres for the various organic functions are situated in it, as the Respiratory ceiitre, Convulsive centre, Diatetic centre, centre for Degluta- . tion. Vomiting centre, etc. The Pons Varolii is intimately connected with the co-ordination of the movements. The Cerebellum regulates and co-ordinates the mus- cular movements of the body. The Cerebrum is the organ of intellectual action, emotion and volition. Cranial Nerves. The nerves which are transmitted through the fora- mina at the base of the cranium, are called cranial nerves. They leave in pairs regularly deposed, one on the right and one on the left side, and are named numerically, according to the order in which they leave the cavity, and by names derived from the parts jj, ;-ii —106- to which they are distributed, or the functions they perform. There are 12 pairs. 1st. — The Olfactory, or nerve of special sense of sniell, is distributed to the mucous membrane of the posterior part of the nasal fossa. 2nd. — The Optic, or nerve of special sense of sight, enters the eye and expands into the retina. 3rd. — Motors Ociiloruin, a motor nerve, is distrib- uted to most of the muscles of the eye. 4th. — Pathetic, a motor nerve, the smallest of the 12, is distributed to the superior oblique muscle of the eye. 5th. — Trifacial, a nerve of common sensation and motion and indirectly of special sense, is the large^^t cranial nerve, and belongs to the class of mixed nerves. It is divided into three branches, viz., the Ophthalmic, Superior Maxillary and Inferior Maxillary branches. The Ophthahnic subdivides into the frontal, lachrymal and nasal. The frontal is distributed to the skin of the forehead and the muscles above the eve. The lachrymal to the lachrymal gland, and muscles and skin of the anterior part of the ear. The nasal to the pituitary membrane on the walls of the nasal fossa; it gives a branch to the menibrana nictitans and one to the lach- rymal sac. The Superior Ma^rillary branch subdivides into the Orbital, Anterior Palatine, Posterior Palatine. Nasal and Dental branches, which supply the pp' their names ind cate. The Inferior Maxillary brancn is the largest of the three and .subdivides into the Mas- seter, Buccal, Internal Plerygoidean, Lingual, Mylo hyoidean and Dental branches. The lingual is the nerve of the special sense of taste. 6tli. — Ahducens, a motor nerve, supplies the abductor oculi and the external portion of retractor oculi muscles. 7th. — Facial, a motor nerve, goes to the muscles of the face. 8th. — Auditory, the nerve of special sense of hearing, supplies the internal ear. 9th. — G lasso Pharyngeal is a mixed nerve distribut- ed principally to the tongue and pharynx. 10th. — Pneuinogastric, a mixed nerve, is remarkabie for its extent, and for the numerous dissimilar organs it supplies It gives branches to the various respira- —107- .•7 tor}' organs and to the stomach and ciesopha^^us. II also gives branches to the heart and lungs. It anasii- moses freely with other cerebro spinal and with the sympathetic nerves. 11th. — Spinal accessory, a motor nerve, arises from the whole extent of the cervical portion of the si)ina] cord and receives fillaments from the brain. It is dis- tributed chiefly to the muscles of the neck and shoulders. 12th. — Hypo Glossal is a motor nerve, and is dis- tributed to the muscles of the tongue. Spinal Nerves. The nerves which eminate from the spinal cord and make their exit through the intervertebral foramina are collectively known as the spinal nerves. They consist of from 42 to 43 pairs and are divided according to the regions into S cervical, 17 dorsal, 6 lumbar, 5 sacral, and 6 or 7 coccygeal pairs. The whole of the spinal nerves originate by two orders of roots, superior or sensory, and inferior or motor roots. The former are larger and more numerous, arising from the super- ior lateral fissure, and the latter from the inferior lat- eral fissure of the cord. In the intervertebral foramina there is a ganglion on each of the superior roots under- neath which the inferior root passes. The union of the two roots constitute the spinal nerve which, immed- iately on passing through the foramen divides into 2 branches, a superior distributed to the spinal muscles and skin which covers them, and an inferior, longer and larger, distributed to the inferior and lateral parts of the trunk, and in some cases to the extremities. The spinal nerve sends various communicating branches to the S3'mpathetic system. Sympathetic System. The Spmpathetic, or ganglionic system of nerves, the nerves of organic life, consists of two large cords or chains of nerves, which extend from the he ul to the posterior extremity of the sacrum, under the lateral parts of the borders of the vertebrte on each side of the columns. These nerve cords are furnished with a number of ganglia, wdiich both give and receive num- erous communicating filaments from the cerebro spinal nerves. A sympathetic ganglion is a nerve centre —108— to which converge various so-called afferent branches, motor, sensory, and sympathetic, while the filaments which leave the ganglion to supply the various organs are known as emergent or efferent branches, which thus exercise a mixed and varied function. They sup- ply the blood vessels, glands and viscera. The sym- pathetic system is divided into five regions, viz., the Cephalic, Cervical, Dorsal or thoracic, Ivumbar or ab- dominal, and Sacral or pelvic, Aesthesiolo^y. We will now consider the organs of special sense and common sensation. The Ear. The apparatus of hearing is composed of 3 parts, viz., the external, middle and internal ear, the two first being accessor}', for the collection and transmission of sound, and the latter the essential organ, which receives the impressions thus conveyed. The external ear consists of the concha, or project- ing shell-like orifice, and the meatus auditorius exter- nus, or passage which extends from the concha to the tympanic membrane bounding the cavity. It is partly osseous and partly cartilaginous, and is narrower in the middle than at either extremity. Its lining is a continuation of the skin of the concha, and it gradually becomes thinner as it descends, and is perforated by a number of small openings from the cermninous glands which secrete the wax of the ear. The cartilages of the external ear are the conchal, annular and the scuti- forni. The mobility of the organ in the solipedes is so great that it is regarded as the chief organ of expres- sion. The middle ear, or tympanum, is an irregular long cavity within the petrosal bone. It is bounded extern- ally by the membrana tympani, or drum of the ear; internalh' by the bony walls of the internal ear, anter- iorly by the Eustachian tubes, and posteriorly by the mastoid cells. A chain of bones, the auditory ossicles, stretch across the tympanum. They are the malleus, incus, stapes and lenticular bone or os orbiculare . The cavity is filled with air and communicates with the pharynx by the Eustachian tubes. The chain of bones transmits the impression received from the membrani t3'mpanni to the internal ear, upon which the auditory nerve is distributed. 'M —109— The internal ear, or labyrinth, is the ultiiiiate part of the organ of hearing, and consists of the vestibule, semi-elrenlar canals and each lea. It consists of a series of cavities hollowed out of the petrous portion of the temporal bone communicating externally with the middle ear through the fenestra oralis and fenestra rotunda, and internally with the cranial cavity through the meatus auditoriiis internus, which transmits th auditory nerve. The Eye. The apparatus of vision comprises the essential organ, the globe of the eye or eye-ball, and its acces- sory parts or appendages. The fflohe of the eye is spherical in form, having the segment of a smaller sphere engrafted on its anterior surface, and increasing its antero-posterior diameter. It consists of a mem- branous sac containing certain transparent humours of different densities, which serve as refracting media. It is attached to the orbit by the muscles which move it, and reposes on a cushion of fat which not only maintains it in its proper position, but also assists in steadying its movements. The Tunies of the eye are three in number: 1st, the Scleoric and Cornea; 2nd, the Choroid and I)is\ and 3rd, the Retina. The sclerotic coat and cornea form the external tunic. Four-fifths of the globe are inve.st- ed by the sclerotic, the remaining one- fifth by the cornea. The sclerotic coat is a dense white fibrous membrane, which extends from the insertion of the optic nerve to the cornea. Its external surface is in connection with the cellular and adipose tissue and with the muscles of the eye ball, the tendons of which expand over it and form a thin tendinous layer, the tunica albuginea, which is partly covered by the conjunctiva and forms the white of the eye. Its internal surface is attached to the choroid coat by cellular tissue. Its an- terior opening is elliptical, and presents a bevelled edge, which receives the cornea in the manner which a w'atch glass is received by the groove in its case. Posteriorly it is pierced for the passage of the optic and ciliary nerves and the ciliary arteries. The Cornea is composed of 2 layers, the cornea propria and the cornea elastica. It is transparent and —110- elliptical and fits into the groove in the sclerotic. Its anterior surface is convex, its posterior concave. The second tunic of the eye-ball is formed by the choroid and iris. The choroid coat is a thin, vascular membrane of a brownish or black color. It is com- posed of three layers, external, middle and internal. The external consists principally of veins, "vena vor- ticosa,^' with pigment cells, to which its color is due. The middle layer is formed by the ciliary arteries, which form a fine capillary plexus called the tunica Ruyschiana. The internal, or pigmentary layer, is composed of hexagonal cells, containing black pigment granules. On the posterior wall the black pigment is absent, causing a peculiar bluish lUvStre, which, owing to its brilliancy, has received the name of the tape turn Incidtim. The ciliary viuscle is a white ring of fibres which forms the bond of union between the external and middle tunic of the eye. The ciliary processes, from 60 to 80 in number, are arranged in a circle, and are formed by the plating or folding in- wards of the middle and inner layers of the cornea. Their circumference is attached to the ciliary muscle and their central border is received between corres- ponding folds of the suspensory ligament of the crys- talline lens or zonula of Zinn. The Iris is a thin diaphragm or curtain, suspended immediately in front of the crystalline lens, its peri- phery being connected with the choroid coat and ciliar}' muscle, and its centre being pierced by an elliptical opening, the pupil. It is variously colored, but in the horse is generally brown, with more or less of a yellow tinge, but sometimes it is almost white or grey, when the animal is said to be "wall-eyed." Its anterior surface is slightly convex, and its posterior surface covered with a deep purple ligament, called the uvea, from its resemblance in color to a ripe grape. Two sets of fibres enter into the formation of the iris, one of which, converging from the circumference to the cen- tre, has the power of dilating the pupil ; the o^her, surrounding the margin of the pupil on its posterior surface and blending with the radiating fibres, has the power of contracting it. The small bodies on the upper pupillary margin of the iris, three or four in number. ■Ill- are the corpora ni_i^ra, their use appearing to be that of conceiUratiuK the rays of light, and preventing their top direct passage through tlie pupil. The third tunic is the retina which is prolonged for- wards to the ciliary processes. It is the terminal ex- pansion of the optic nerve over the internal surface of the choroid coat from which it is easily separated. It consists of 9 lavers, viz.: 1st, Internal limiting layer; 2nd, Optic nerve fibres; 3rd, Ganglionic cells; 4th, Internal molecular layer; 5tli, Internal granular layer; 6th, External molecular layer; 7th, External granular layer; 8th, External lining membrane; 9th, IJasilary layer, or rods and cones. The Ciliary zone, or Zonula of Zinn, is a thin va.scular layer which connects the anterior margin of the retina with the anterior surface of the lens, and presents a number of folds which are received between corresponding folds of the ciliary processes. Humours of the Eye. These, the reflecting media, are 3 in nuni])er, viz. : the aqueous and vitreous humours, and the crystalline lens. The Aqueous humour consists chiefly of water with an alkaline reaction, and completely fills the anterior and posterior chambers of the eye ; both chambers are lined by a serous membrane which secretes the aqueous humour. The anterior chamber is the space between the internal surface of the cornea and the iris, pupil and ciliary muscle. The posterior chamber is the nar- row space bounded in front by the iris, and behind by the capsule of the lens. The Vitreous humour occupies about four-fifths of the whole interior of I he globe. It is a highly albu- minous and perfectly transparent substance of the con- sistance of jelly, enclosed in a delicate membrane, the hyaloid, from the inner surface of which numerous lamella are sent inwards to form the compartments in which the fluid portion is contained. If this fluid es- capes, or be destroyed, it will not be reproduced. The Crystalline humour, or lens, is situated immed- iately behind the pupil, in front of the vitreous humour, and is surrounded by the ciliary processes which slight- ly overlap its margin. It is bi convex, the convexity m -112- o( the posterior face being the greater, and is enveloped by a transparent elastic membrane, the capsule of the lens. It is constrncted of concentric layers of lamina;, of which the external are soft and the internal firmer. It is supported in its place by the ciliary zone. The motor muscles of the globe of the eye are seven, five <»f which are s/rcn[i>/i/, the other two oblique. The superior oblique elevates and rotates the eye-ball. The inferior depresses and turns the eye inwards. The AppLii(f(i,i>es of the eye are the eye-brows, ej'e- lids, membrana nicitans, conjunctiva, caruncula lacli- rymalis, lachr3'mal apparatus and ocular slieath. The eye-bro7vs, very rudimentary in the horse, are the eminences formed by the orbital processes of the frontal bones. They are furnished with a few long hairs and serve to interrupt too vivid rays of light and to exclude foreign bodies from the eye. The eye-lids are two movable curtains, superior and inferior, which protect the eye. PCntering into their structure are skin, muscles, fibrous tissue, tarsal carti- lage, Meibomian glands and conjunctiva. The tarsal cartilages form the frame work of the free borders of the eye- lids, and are attached to the bones of the orbit by the fibrous tissue. The JMeiboiniau glands are situ- ated between the tarsal cartilages and conjunctiva, and they secrete a fluid which prevents the eye-lids adher- ing together during sleep. The Conjunctiva, the mucous membrane of the eye, is very thin and very vascular. It lines the entire sur- face of the eye-lids, being continuous with the skin, covers the anterior part of the membrana nictitans and passes down the nasal duct. It is reflected over the whole anterior surface of the globe. ^v The Membrana Nictitans, or accessor}^ eye-lid, is situated near the nasal angle between the globe and the side of the orbit. It is composed of elastic fibro cartilage and is irregular in form. Posteriorly it is continuous with the pad of fat which is insinuated be- tween all the muscles of the eye When the eye is in its natural position only the margin of the membrane can be seen, but when, by contraction of the straight muscles, the globe is drawn back, pressing on the pad of fat, the membrane is pressed more or less over the anterior surface of the eye. The movement, which is —113— instantaneous, is for the jnirpose of reuiovinj^ foreij^n bodies from the eye. The caninciila lachrymali^ is a small, round, red- dish ])ody, seen in the inner canthus. Its use is to direct the tears to the laehrynial canals. The Lachrymal .l/yparalus consists of the lachrymal gland, lachrymal canals, lachrvmal sac and nasal duct. T\\Q }>^land is situated in the superior part of the eye and secretes the tears destined to lubricate the anterior sur- face of the eye. The secretion is carried to the inner canthus where it enters the larhryDial canals, which carry it to the sac, a reservoir lodj{ suet, wliich is dis- charged into the hair sacs, The Sudoriferous, or sweat j^lands, are situated in the subcutaneous areolar tissue, surrounded by a quan- tity of fat. They are small round bodies, each of which consi.sth of one or more small tubes coiled into a ball ; the free end of the tube opens on the surface by a funnel shaped orifice. The skin of the horse is characterised by its jjreat sensitiveness, which is still further promoted by grooming and artificial protection. Few animals, if any, perspire as freely as the horse. The large quantity of pigment found in the skin is sup- posed to serve as a protection against the heat of the sun. An epithelial excresence appears in the distal part of the forearm internally, and on the proximal portion of the metatarsus, also internally. These (ergots or chesnuts) according to Chauveau, represent the vestige of the thumb. Hair is an appendage of the skin and in most mam- mals forms the external covering. It is a special modi- fication of the epidermis, having in its bulk the same essential structure ; a hair consists of a root, shaft and point. The root has a bulbous enlargement at its ex- tremity, and is lodged in a recess or hair follicle \ at the bottom of each follicle is a conical vascular papilla similar in every respect to those on the surface of the skin. This papilla fits into a corresponding depression in the root of the hair. The ducts ot one or more sebaceous glands enter into the follicle. About the muzzle of the horse are a number of largely developed strong hairs, commonly known as the cat hairs, from their resemblance to the whiskers of the cat. These are media of touch, their bulbs receiving filaments of sensory nerves. The Foot. (In equine anatomy the foot implies the hoof, with the bones and soft structures it contains.) The study of the foot is of great practical importance, owing to the many diseases and injuries to which it is subject. It resolves itself into the consideration of the V —115— hoof, or horny case, and the parts contained within it. JJy maceration the hoof is divisahle into 3 parts, the wall, »ole and frojjj. The U'd// is that part which is visible when the foot rests on the j^round, an